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Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
from 2018-03-21 to 2018-11-02
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Version / remarks:
2000
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: MEP, RP, China. The Guidelines for the Testing of Chemicals: No. 106 "Adsorption-Desorption using a batch equilibrium method"
Version / remarks:
2013
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
batch equilibrium method
Media:
soil
Radiolabelling:
no
Test temperature:
25°C
Analytical monitoring:
yes
Details on sampling:
The aqueous phase (red soil, black soil, moisture soil and aquic brown soil), was removed and an equal volume of 0.01 M CaCl2 solution without test item was added to the soil phase. The sample was agitated for desorption equilibration time at 20~25 °C. The sample was centrifugated at 5000 r/min for 3 minutes and the centrifugal volume was recorded. The concentration of the aqueous phase was determined.
Matrix no.:
#1
Matrix type:
other: Black Soil
% Clay:
33.4
% Silt:
25.9
% Sand:
40.7
% Org. carbon:
1.16
pH:
6.54
CEC:
28.2 other: c mol/kg
Matrix no.:
#2
Matrix type:
other: Red Soil
% Clay:
44.5
% Silt:
14.3
% Sand:
41.2
% Org. carbon:
0.57
pH:
5.02
CEC:
12.7 other: c mol/kg
Matrix no.:
#3
Matrix type:
other: Paddy Soil
% Clay:
18.1
% Silt:
17.1
% Sand:
64.8
% Org. carbon:
1.14
pH:
6.88
CEC:
1.9 other: c mol/kg
Matrix no.:
#4
Matrix type:
other: Moisture Soil
% Clay:
19.9
% Silt:
17.9
% Sand:
62.2
% Org. carbon:
0.38
pH:
7.82
CEC:
1.9 other: c mol/kg
Matrix no.:
#5
Matrix type:
other: Aquic Brown Soil
% Clay:
40.7
% Silt:
42.8
% Sand:
16.5
% Org. carbon:
1.19
pH:
5.47
CEC:
7.3 other: c mol/kg
Details on matrix:
Five typical soils (red soil, black soil, paddy soil, moisture soil and aquic brown soil) differing in texture, clay content, organic matter content and pH value as the test soils are selected. The soils are sieved through 2 mm mesh sieve and stored under room temperature.
Sample No.:
#1
Duration:
24 h
Initial conc. measured:
>= 8 - <= 800 other: mg/L
Temp.:
>= 20 - <= 25 °C
Sample No.:
#2
Duration:
4 h
Initial conc. measured:
>= 8 - <= 800 other: mg/L
Temp.:
>= 20 - <= 25 °C
Sample No.:
#3
Duration:
4 h
Initial conc. measured:
>= 8 - <= 800 other: mg/L
Temp.:
>= 20 - <= 25 °C
Sample No.:
#4
Duration:
16 h
Initial conc. measured:
>= 8 - <= 800 other: mg/L
Temp.:
>= 20 - <= 25 °C
Sample No.:
#5
Duration:
4 h
Initial conc. measured:
>= 8 - <= 800 other: mg/L
Temp.:
>= 20 - <= 25 °C
Sample No.:
#1
Type:
log Koc
Value:
4.8 dimensionless
pH:
5.02
Temp.:
25 °C
Matrix:
Red Soil
% Org. carbon:
0.57
Sample No.:
#2
Type:
log Koc
Value:
3.1 dimensionless
pH:
6.54
Temp.:
25 °C
Matrix:
Black Soil
% Org. carbon:
1.16
Sample No.:
#3
Type:
log Koc
Value:
2.7 dimensionless
pH:
6.88
Temp.:
25 °C
Matrix:
Paddy Soil
% Org. carbon:
1.14
Sample No.:
#4
Type:
log Koc
Value:
2.7 dimensionless
pH:
7.82
Temp.:
25 °C
Matrix:
Moisture Soil
% Org. carbon:
0.38
Sample No.:
#5
Type:
log Koc
Value:
3.4 dimensionless
pH:
5.47
Temp.:
25 °C
Matrix:
Aquic Brown Soil
% Org. carbon:
1.19
Adsorption and desorption constants:
Red Soil: KFads = 323.15; KFdes =1220
Black Soil: KFads = 15.111; KFdes = 24.044
Paddy Soil: KFads=6.080; KFdes =19.342
Moisture Soil: KFads=1.831; KFdes =13.158
Aquic Brown Soil: KFads=29.888; KFdes =43.521
Sample no.:
#1
Duration:
24 h
% Adsorption:
58
Sample no.:
#2
Duration:
4 h
% Adsorption:
68.4
Sample no.:
#3
Duration:
4 h
% Adsorption:
47.7
Sample no.:
#4
Duration:
16 h
% Adsorption:
32.5
Sample no.:
#5
Duration:
4 h
% Adsorption:
74.5
Sample no.:
#1
Duration:
48 h
% Desorption:
20.6
Sample no.:
#2
Duration:
24 h
% Desorption:
-2.8
Sample no.:
#3
Duration:
24 h
% Desorption:
-15.4
Sample no.:
#4
Duration:
24 h
% Desorption:
-2
Sample no.:
#5
Duration:
24 h
% Desorption:
4.3
Transformation products:
not measured
Validity criteria fulfilled:
yes
Conclusions:
The substance has log Koc in soil types ranging from 2.7 - 4.8. Depending on the soil type, the substance is moderately to strongly absorbing to soil.

Description of key information

The substance has log Koc in 5 soil types ranging from 2.7 - 4.8. Depending on the soil type, the substance is moderately to strongly absorbing to soil. The highest log Koc is considered the worst case for the CSA. The log Koc was determined in an OECD 106 guideline study.

Key value for chemical safety assessment

Koc at 20 °C:
56 693

Additional information