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Endpoint:
adsorption / desorption: screening
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:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Deviations:
no
Qualifier:
according to
Guideline:
other: U. S. EPA, Fate, Transport and Transformation Test Guidelines, OPPTS 835.1230, “Adsorption/Desorption (Batch Equilibrium)”, October 2008.
Deviations:
no
GLP compliance:
yes
Type of method:
batch equilibrium method
Media:
soil
Radiolabelling:
yes
Test temperature:
20 ± 2°C
Analytical monitoring:
yes
Details on sampling:
- Concentrations: To determine test item stability, 50 to 200 µL aliquot of the adsorption supernatant of one replicate of each soil from the highest test concentration (nominal 5-µg/mL) was analysed
- Sample storage before analysis: Test item stock solution and the treatment solutions were all stored frozen. The aqueous and soil phase samples were all stored frozen after collection.
Matrix no.:
#1
Matrix type:
sandy loam
% Clay:
9
% Silt:
29
% Sand:
62
% Org. carbon:
1.7
pH:
7.6
CEC:
9.8 meq/100 g soil d.w.
Bulk density (g/cm³):
1.12
Matrix no.:
#2
Matrix type:
silty clay loam
% Clay:
36
% Silt:
54
% Sand:
10
% Org. carbon:
1.9
pH:
5.9
CEC:
18.6 meq/100 g soil d.w.
Bulk density (g/cm³):
1.02
Matrix no.:
#3
Matrix type:
clay
% Clay:
47
% Silt:
39
% Sand:
14
% Org. carbon:
2
pH:
7.5
CEC:
17.4 meq/100 g soil d.w.
Bulk density (g/cm³):
1.06
Matrix no.:
#4
Matrix type:
loam
% Clay:
14
% Silt:
50
% Sand:
36
% Org. carbon:
1.2
pH:
7
CEC:
11.3 meq/100 g soil d.w.
Bulk density (g/cm³):
1.15
Matrix no.:
#5
Matrix type:
sandy loam
% Clay:
2
% Silt:
32
% Sand:
66
% Org. carbon:
3.1
pH:
5.4
CEC:
8.2 meq/100 g soil d.w.
Bulk density (g/cm³):
1.09
Details on matrix:
COLLECTION AND STORAGE
- Soil preparation: Prior to use, the test soils were air-dried and sieved through a 2-mm sieve. Triplicate 5-g aliquots of each soil were dried overnight in an oven at approximately 105°C.
Details on test conditions:
TEST SYSTEM
- Type, size and further details on reaction vessel: The test system consisted of individually capped test vessels containing the soil and the test solution, continuously agitated using a mechanical shaker to keep the soil in suspension during equilibration.
- Number of reaction vessels/concentration: 5 duplicates were used.
- Method of preparation of test solution: The stock solution was prepared in acetonitrile. The required volume of stock solution was evaporated to dryness using a gentle stream of nitrogen. The residue was reconstituted with aqueous 0.01 M CaCl2 solution.
- Are the residues from the adsorption phase used for desorption: Yes
- Soil-to-Solution Ratio: 1 : 4
Sample No.:
#1
Duration:
24 h
Initial conc. measured:
>= 0.05 - <= 5 other: µg a.i./mL
Temp.:
20 °C
Remarks:
Nominal test concentrations: 0.05, 0.1, 0.5, 1 and 5 µg/mL
Sample No.:
#2
Duration:
24 h
Initial conc. measured:
>= 0.05 - <= 5 other: µg a.i./mL
Temp.:
20 °C
Remarks:
Nominal test concentrations: 0.05, 0.1, 0.5, 1 and 5 µg/mL
Sample No.:
#3
Duration:
24 h
Initial conc. measured:
>= 0.05 - <= 5 other: µg a.i./mL
Temp.:
20 °C
Remarks:
Nominal test concentrations: 0.05, 0.1, 0.5, 1 and 5 µg/mL
Sample No.:
#4
Duration:
24 h
Initial conc. measured:
>= 0.05 - <= 5 other: µg a.i./mL
Temp.:
20 °C
Remarks:
Nominal test concentrations: 0.05, 0.1, 0.5, 1 and 5 µg/mL
Sample No.:
#5
Duration:
24 h
Initial conc. measured:
>= 0.05 - <= 5 other: µg a.i./mL
Temp.:
20 °C
Remarks:
Nominal test concentrations: 0.05, 0.1, 0.5, 1 and 5 µg/mL
Sample no.:
#1
Duration:
24 h
Conc. of adsorbed test mat.:
36.13 other: µg
Temp.:
20 °C
Remarks:
Replicate 1
Sample no.:
#1
Duration:
24 h
Conc. of adsorbed test mat.:
35.68 other: µg
Temp.:
20 °C
Remarks:
Replicate 2
Sample no.:
#2
Duration:
24 h
Conc. of adsorbed test mat.:
67.18 other: µg
Temp.:
20 °C
Remarks:
Replicate 1
Sample no.:
#2
Duration:
24 h
Conc. of adsorbed test mat.:
68.05 other: µg
Temp.:
20 °C
Remarks:
Replicate 2
Sample no.:
#3
Duration:
24 h
Conc. of adsorbed test mat.:
41.92 other: µg
Temp.:
20 °C
Remarks:
Replicate 1
Sample no.:
#3
Duration:
24 h
Conc. of adsorbed test mat.:
40.32 other: µg
Temp.:
20 °C
Remarks:
Replicate 2
Sample no.:
#4
Duration:
24 h
Conc. of adsorbed test mat.:
37.51 other: µg
Temp.:
20 °C
Remarks:
Replicate 1
Sample no.:
#4
Duration:
24 h
Conc. of adsorbed test mat.:
39.21 other: µg
Temp.:
20 °C
Remarks:
Replicate 2
Sample no.:
#5
Duration:
24 h
Conc. of adsorbed test mat.:
61.04 other: µg
Temp.:
20 °C
Remarks:
Replicate 1
Sample no.:
#5
Duration:
24 h
Conc. of adsorbed test mat.:
58.4 other: µg
Temp.:
20 °C
Remarks:
Replicate 2
Key result
Sample No.:
#1
Type:
Kd
Value:
3.78 other: mL/g
Temp.:
20 °C
Matrix:
Nambsheim (sandy loams)
% Org. carbon:
1.7
Key result
Sample No.:
#2
Type:
Kd
Value:
11.9 other: mL/g
Temp.:
20 °C
Matrix:
Tama (silty clay loam)
% Org. carbon:
1.9
Key result
Sample No.:
#3
Type:
Kd
Value:
4.23 other: mL/g
Temp.:
20 °C
Matrix:
Lleida (clay)
% Org. carbon:
2
Key result
Sample No.:
#4
Type:
Kd
Value:
4.14 other: mL/g
Temp.:
20 °C
Matrix:
Gross-Umstadt (loam)
% Org. carbon:
1.2
Key result
Sample No.:
#5
Type:
Kd
Value:
10.3 other: mL/g
Temp.:
20 °C
Matrix:
Sassafras (sandy loams)
% Org. carbon:
3.1
Key result
Sample No.:
#1
Type:
Koc
Value:
223 other: mL/g
Temp.:
20 °C
Matrix:
Nambsheim (sandy loams)
% Org. carbon:
1.7
Key result
Sample No.:
#2
Type:
Koc
Value:
629 other: mL/g
Temp.:
20 °C
Matrix:
Tama (silty clay loam)
% Org. carbon:
1.9
Key result
Sample No.:
#3
Type:
Koc
Value:
212 other: mL/g
Temp.:
20 °C
Matrix:
Lleida (clay)
% Org. carbon:
2
Key result
Sample No.:
#4
Type:
Koc
Value:
345 other: mL/g
Temp.:
20 °C
Matrix:
Gross-Umstadt (loam)
% Org. carbon:
1.2
Key result
Sample No.:
#5
Type:
Koc
Value:
333 other: mL/g
Temp.:
20 °C
Matrix:
Sassafras (sandy loams)
% Org. carbon:
3.1
Adsorption and desorption constants:
The Kd values ranged from 2.13-5.23 mL/g in the Nambsheim soil, 7.57-16.4 mL/g in the Tama soil, 2.58-5.68 mL/g in the Lleida soil, 2.30-5.60 mL/g in the Gross-Umstadt soil and 5.72-14.0 mL/g in the Sassafras soil. The adsorption coefficients were normalized to the organic matter and organic carbon contents for each test soil to calculate the soil sorption coefficients Kom and Koc, respectively. The Kom values ranged from 73.4-180 mL/g in the Nambsheim soil, 229-497 mL/g in the Tama soil, 73.7-162 mL/g in the Lleida soil, 115-280 mL/g in Gross-Umstadt soil and 106-259 mL/g in the Sassafras soil, while the Koc values ranged from 125-308 mL/g in the Nambsheim soil, 398-863 mL/g in the Tama soil, 129-284 mL/g in the Lleida soil, 192-467 mL/g in the Gross-Umstadt soil and 185-452 mL/g in the Sassafras soil.
The value of the Freundlich adsorption isotherm parameter, KF, was 2.75, 8.51, 3.28, 3.06 and 7.19 for the Nambsheim, Tama, Lleida, Gross-Umstadt and Sassafras soils, respectively. The KFom values were 94.8, 258, 93.7, 153 and 133 while the KFoc values were 162, 448, 164, 255 and 232 for Nambsheim, Tama, Lleida, Gross-Umstadt and Sassafras soils, respectively. The values for the Freundlich constant, 1/n, were 0.8219, 0.8620, 0.8582, 0.8337 and 0.8485 for Nambsheim, Tama, Lleida, Gross-Umstadt and Sassafras soils, respectively. The correlation coefficient (R²) for the analyses were 0.9989, 0.9995, 0.9991, 0.9977 and 0.9976 for Nambsheim, Tama, Lleida, Gross-Umstadt and Sassafras soils, respectively, for the adsorption phase, indicating the Freundlich equation adequately predicts the adsorption of the test item over the concentration range studied.
The mean desorption Kd, values ranged from 3.33 mL/g in the Nambsheim soil to 11.0 mL/g in the Tama soil. The mean desorption Kd,om values ranged from 110 mL/g in the Lleida soil to 333 mL/g in the Tama soil. The mean desorption Kd,oc values ranged from 192 mL/g in the Lleida soil to 579 mL/g in the Tama soil.
Sample no.:
#1
Duration:
48 h
% Desorption:
61.6
Remarks on result:
other: total % desorbed
Sample no.:
#2
Duration:
48 h
% Desorption:
39
Remarks on result:
other: total % desorbed
Sample no.:
#3
Duration:
48 h
% Desorption:
58
Remarks on result:
other: total % desorbed
Sample no.:
#4
Duration:
48 h
% Desorption:
58.7
Remarks on result:
other: total % desorbed
Sample no.:
#5
Duration:
48 h
% Desorption:
43.4
Remarks on result:
other: total % desorbed
Transformation products:
no
Details on results (Batch equilibrium method):
PRELIMINARY TEST
- Sample purity: 100.00%
- Volume of CaCl2 solution: 18 to 20mL
- Initial test substance concentration: 5.736 µg/mL
- Test substance concentration in final solution: 5.603 µg/mL

MAIN TEST: PERFORMANCE
- Test material stability during adsorption/desorption phase: 100.00%
- Experimental conditions maintained throughout the study: Yes
Conclusions:
The Kd values ranged from 2.13-5.23 mL/g in the Nambsheim soil, 7.57-16.4 mL/g in the Tama soil, 2.58-5.68 mL/g in the Lleida soil, 2.30-5.60 mL/g in the Gross-Umstadt soil and 5.72-14.0 mL/g in the Sassafras soil.
The total percent desorbed (DT) values ranged from 39.0% in the Tama soil to 61.6% in the Nambsheim soil. In general, lower desorption values were observed in second desorption interval. The highest desorption was observed in Nambsheim and Gross-Umstadt soils in first and second desorption intervals respectively. In both the desorption intervals, the lowest desorption was observed in Tama soil.
Executive summary:

The adsorption and desorption properties of test substance to five different soils were investigated in the laboratory. The adsorption coefficients (Kd, Kom, and Koc), the desorption coefficients (Kd1, Kd2, Kd1,om, Kd1,oc, Kd2,om and Kd2,oc) and the Freundlich adsorption isotherm parameters (KF, KFom, KFoc and 1/n) were calculated.

The texture of the soils included two sandy loams (Nambsheim and Sassafras), a silty clay loam (Tama), a clay (Lleida) and a loam (Gross-Umstadt). The per cent organic matter (Walkley-Black method) of the soils ranged from 2.0 to 5.4% and the pH in aqueous 0.01 M CaCl2 ranged from 5.1 to 7.5.

The study was conducted as per procedures outlined in OECD Guideline 106 and U. S. EPA test guidelines OPPTS 835.1230.

The adsorption experiment was performed using the batch equilibration method on the soils with five nominal test concentrations (0.05, 0.1, 0.5, 1 and 5 µg/mL) of the test item prepared in aqueous 0.01 M CaCl2. Two desorption cycles were performed on samples treated at the highest test concentration. A 1:4 (w/v) soil-to- solution ratio was used in the preliminary and definitive experiments. The sorption coefficients Kd, Kom and Koc were calculated for each soil at each test concentration.

The Kd values ranged from 2.13-5.23 mL/g in the Nambsheim soil, 7.57-16.4 mL/g in the Tama soil, 2.58-5.68 mL/g in the Lleida soil, 2.30-5.60 mL/g in the Gross-Umstadt soil and 5.72-14.0 mL/g in the Sassafras soil. The adsorption coefficients were normalized to the organic matter and organic carbon contents for each test soil to calculate the soil sorption coefficients Kom and Koc, respectively. The Kom values ranged from 73.4-180 mL/g in the Nambsheim soil, 229-497 mL/g in the Tama soil, 73.7-162 mL/g in the Lleida soil, 115-280 mL/g in Gross-Umstadt soil and 106-259 mL/g in the Sassafras soil, while the Koc values ranged from 125-308 mL/g in the Nambsheim soil, 398-863 mL/g in the Tama soil, 129-284 mL/g in the Lleida soil, 192-467 mL/g in the Gross-Umstadt soil and 185-452 mL/g in the Sassafras soil.

The value of the Freundlich adsorption isotherm parameter, KF, was 2.75, 8.51, 3.28, 3.06 and 7.19 for the Nambsheim, Tama, Lleida, Gross-Umstadt and Sassafras soils, respectively. The organic matter and organic carbon normalized Freundlich adsorption isotherm coefficients KFom and KFoc, respectively, were calculated for all the soils. The KFom values were 94.8, 258, 93.7, 153 and 133 while the KFoc values were 162, 448, 164, 255 and 232 for Nambsheim, Tama, Lleida, Gross-Umstadt and Sassafras soils, respectively. The values for the Freundlich constant, 1/n, were 0.8219, 0.8620, 0.8582, 0.8337 and 0.8485 for Nambsheim, Tama, Lleida, Gross-Umstadt and Sassafras soils, respectively. The correlation coefficient (R²) for the analyses were 0.9989, 0.9995, 0.9991, 0.9977 and 0.9976 for Nambsheim, Tama, Lleida, Gross-Umstadt and Sassafras soils, respectively, for the adsorption phase, indicating the Freundlich equation adequately predicts the adsorption of the test item over the concentration range studied.

The mean desorption Kd, values ranged from 3.33 mL/g in the Nambsheim soil to 11.0 mL/g in the Tama soil. The mean desorption Kd,om values ranged from 110 mL/g in the Lleida soil to 333 mL/g in the Tama soil. The mean desorption Kd,oc values ranged from 192 mL/g in the Lleida soil to 579 mL/g in the Tama soil.

The total per cent desorbed (DT) values ranged from 39.0% in the Tama soil to 61.6% in the Nambsheim soil. In general, lower desorption values were observed in second desorption interval. The highest desorption was observed in Nambsheim and Gross-Umstadt soils in first and second desorption intervals respectively. In both the desorption intervals, the lowest desorption was observed in Tama soil.

Endpoint:
adsorption / desorption, other
Remarks:
Adsorption Coefficient Study
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Deviations:
no
Qualifier:
according to
Guideline:
other: MAFF 12-Nousan-8147
Deviations:
no
GLP compliance:
no
Type of method:
other: Adsorption isothermal test
Media:
soil
Radiolabelling:
no
Test temperature:
25 ± 2°C
Analytical monitoring:
yes
Matrix no.:
#1
Matrix type:
other: Sandy soil
% Clay:
3.5
% Silt:
5.4
% Sand:
91.1
pH:
6.2
CEC:
4.6 other: cmolc/Kg
Matrix no.:
#2
Matrix type:
loam
% Clay:
17.9
% Silt:
39.3
% Sand:
42.8
pH:
5.9
CEC:
24.6 other: cmolc/kg
Matrix no.:
#7
Matrix type:
silty clay
% Clay:
46.6
% Silt:
42.3
% Sand:
11.1
pH:
5.9
CEC:
33.3 other: cmolc/kg
Matrix no.:
#8
Matrix type:
other: Silty loam
% Clay:
20.8
% Silt:
54.5
% Sand:
24.7
pH:
7
CEC:
24.9 other: cmolc/kg
Sample No.:
#1
Duration:
24 h
Initial conc. measured:
>= 0.05 - <= 5 other: µg/mL
Temp.:
25 °C
Remarks:
Nominal test concentrations: 0.05, 0.2, 1 and 5 µg/mL
Sample No.:
#2
Duration:
24 h
Initial conc. measured:
>= 0.05 - <= 5 other: µg/mL
Temp.:
25 °C
Remarks:
Nominal test concentrations: 0.05, 0.2, 1 and 5 µg/mL
Sample No.:
#7
Duration:
24 h
Initial conc. measured:
>= 0.05 - <= 5 other: µg/mL
Temp.:
25 °C
Remarks:
Nominal test concentrations: 0.05, 0.2, 1 and 5 µg/mL
Sample No.:
#8
Duration:
24 h
Initial conc. measured:
>= 0.05 - <= 5 other: µg/mL
Temp.:
25 °C
Remarks:
Nominal test concentrations: 0.05, 0.2, 1 and 5 µg/mL
Key result
Sample No.:
#1
Type:
Kd
Value:
0.907 dimensionless
Temp.:
25 °C
Matrix:
Miyazaki (sandy soil)
Key result
Sample No.:
#2
Type:
Kd
Value:
1.64 dimensionless
Temp.:
25 °C
Matrix:
Saitama Okabe (loam)
Key result
Sample No.:
#7
Type:
Kd
Value:
4.3 dimensionless
Temp.:
25 °C
Matrix:
Saitama Shiraoka (silty clay)
Key result
Sample No.:
#8
Type:
Kd
Value:
3.86 dimensionless
Temp.:
25 °C
Matrix:
Ibaraki (silty loam)
Key result
Sample No.:
#1
Type:
Koc
Value:
182 dimensionless
Temp.:
25 °C
Matrix:
Miyazaki (sandy soil)
Key result
Sample No.:
#2
Type:
Koc
Value:
54.3 dimensionless
Temp.:
25 °C
Matrix:
Saitama Okabe (loam)
Key result
Sample No.:
#7
Type:
Koc
Value:
121 dimensionless
Temp.:
25 °C
Matrix:
Saitama Shiraoka (silty clay)
Key result
Sample No.:
#8
Type:
Koc
Value:
176 dimensionless
Temp.:
25 °C
Matrix:
Ibaraki (silty loam)
Adsorption and desorption constants:
The soil adsorption equilibrium constant obtained from the Freundlich adsorption coefficient of the soil and organic carbon content was 89.39, and its correlation coefficient was 0.615.
Recovery of test material:
The average recovery rate of added test substance was 101 to 103% when 0.04 µg/mL was added and 99 to 102% when 2.0 µg/mL was added to the aqueous phase, and 95 to 97% when 50 µg was added to the solid phase.
Sample no.:
#1
Duration:
24 h
% Adsorption:
95.2
Remarks on result:
other: based on the test substance in aqueous phase and solid phase by analyzing the solid phase after 24 hours of stirring when the solution reached equilibrium in the preliminary test (step 1)
Sample no.:
#2
Duration:
24 h
% Adsorption:
96.6
Remarks on result:
other: based on the test substance in aqueous phase and solid phase by analyzing the solid phase after 24 hours of stirring when the solution reached equilibrium in the preliminary test (step 1)
Sample no.:
#7
Duration:
24 h
% Adsorption:
99.4
Remarks on result:
other: based on the test substance in aqueous phase and solid phase by analyzing the solid phase after 24 hours of stirring when the solution reached equilibrium in the preliminary test (step 1)
Sample no.:
#8
Duration:
24 h
% Adsorption:
99.5
Remarks on result:
other: based on the test substance in aqueous phase and solid phase by analyzing the solid phase after 24 hours of stirring when the solution reached equilibrium in the preliminary test (step 1)
Transformation products:
no
Conclusions:
The soil adsorption equilibrium constant obtained from the Freundlich adsorption coefficient of the soil and organic carbon content was 89.39, and its correlation coefficient was 0.615.
Executive summary:

The adsorption of the test substance by soil was tested using four types of soil including volcanic ash soil in a laboratory with the temperature of 25 ± 2°C, stirring temperature at 25°C, and centrifuge temperature at 25 ± 2°C as outlined in the guidelines OECD 106 and MAFF 12-Nousan-8147.

The soil adsorption rate of the test substance after 24 hours became 20.8% to 45.0% when the soil-to-solution ratio was 1:2 for #1 Miyazaki and 1:5 for #2 Saitama Okabe, #7 Saitama Shiraoka, and #8 Ibaraki. The same soil-to-solution ratio was used thereafter.

The mass balance after stirring for 24 hours was favourable and ranged between 95.2 and 99.5%. The adsorption rate on the surface of the container was 0.1%.

Changes in adsorption were observed after stirring for 4, 8, 16, and 24 hours. The change rate was -1 to -4% after 16 to 24 hours and reached the equilibrium before 24 hours. The soil adsorption rate after 24 hours was 24.2 to 45.8%. The pH value was 5.7 to 7.6.

Four types of soil were used for the adsorption isothermal test, and test solutions with the test substance concentrations of 5.0, 1.0, 0.2, and 0.05 µg/mL were stirred for 24 hours. The Freundlich adsorption coefficient (Kf) is 0.915 to 4.79. The Freundlich exponent (1/n) was 0.880 to 0.960. The correlation coefficient (r) was 0.999 for all samples.

The organic carbon adsorption coefficient (Koc) was 50.3 to 197. The soil adsorption equilibrium constant obtained from the adsorption isothermal test of four types of soil was 89.39, and its correlation coefficient was 0.615.

Description of key information

OECD 106

Key value for chemical safety assessment

Koc at 20 °C:
348.4

Additional information

In the OECD Guideline 106 study, the total percent desorbed (DT) values ranged from 39.0% in the Tama soil to 61.6% in the Nambsheim soil. The Koc in the different soils ranged from 212 to 629 mL/g with an average value of 348.4 mL/g.