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Environmental fate & pathways

Adsorption / desorption

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Administrative data

Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2001
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: according Guideline and GLP

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001
Report Date:
2001

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
GLP compliance:
yes (incl. certificate)
Type of method:
batch equilibrium method
Media:
soil

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material: Hostapur SAS 60
- Physical state: paste
- Analytical purity: 60%
- Composition of test material, percentage of components: 60% Hostapur SAS 93, water
- Lot/batch No.: DEADAN 4847
- Expiration date of the lot/batch: 2001-03-20

Study design

Test temperature:
20 +/- 2 °C

Batch equilibrium or other method

Analytical monitoring:
yes
Details on matrix:
The standard EURO soils No. 1, 2, 3, 4 and 5 and one sediment were used. All soils and sediment were sieved containing a maximum particle size of 2 mm.

PROPERTIES
- Soil texture: EURO 1
- % sand: 3.3
- % silt: 21.90
- % clay: 75
- pH: 5.7
- Total carbon: 3.5
- Organic carbon (%): 3.29
- CEC (meq/100 g): 32.4

PROPERTIES
- Soil texture: EURO 2
- % sand: 13.4
- % silt: 64.1
- % clay: 22.6
- pH: 7.2
- Total carbon: 10.9
- Organic carbon (%): 2.39
- CEC (meq/100 g): 28.9

PROPERTIES
- Soil texture: EURO 3
- % sand: 46.4
- % silt: 36.8
- % clay: 17.0
- pH: 5.9
- Total carbon: 3.6
- Organic carbon (%): 3.32
- CEC (meq/100 g): 16.6

PROPERTIES
- Soil texture: EURO 4
- % sand: 4.11
- % silt: 75.7
- % clay: 20.30
- pH: 6.8
- Total carbon: 1.7
- Organic carbon (%): 1.36
- CEC (meq/100 g): 17.3

PROPERTIES
- Soil texture: EURO 5
- % sand: 71.6
- % silt: 12.7
- % clay: 6.00
- pH: 3.2
- Total carbon: 3.7
- Organic carbon (%): 4.43
- CEC (meq/100 g): 24.1

PROPERTIES
- Soil texture: Sediment
- % sand: 95.1
- % silt: 0.9
- % clay: 4.1
- pH: 5.36
- Total carbon: n.d.
- Organic carbon (%): 0.31
- CEC (meq/100 g): 1.28
Details on test conditions:
TEST CONDITIONS
- Suspended solids concentration: soil solution ratio was 1:25 (2 g soil and 50 ml solution) to achive > 20 %

TEST SYSTEM
- Type, size and further details on reaction vessel: 50 ml centrifugation tubes (polypropylene) with screw cap
- Number of reaction vessels/concentration: 2
- Measuring equipment: gas chromatograph and flame ionisation detector
- Method of preparation of test solution: As stock solution, 2 g soil and 50 ml 0.01 M CaCl2 were given into a centifugation tube, closed with the scew cap and shaken over night to equilibrate the soil. Five test item concentrations 20, 40, 60, 80 and 100 mg/L were applied to each soil.
Computational methods:
- Adsorption and desorption coefficients (Kd): differend values for the differend soil types (see tables below)
- Freundlich adsorption and desorption coefficients: differend values for the differend soil types (see tables below)
- Adsorption coefficient per organic carbon (Koc): differend values for the differend soil types (see tables below)

Results and discussion

Adsorption coefficientopen allclose all
Type:
Kd
Remarks:
Soil 1
Value:
50
Temp.:
20 °C
% Org. carbon:
3.3
Type:
Kd
Remarks:
Soil 2
Value:
56
Temp.:
20 °C
% Org. carbon:
2.4
Type:
Kd
Remarks:
Soil 3
Value:
35
Temp.:
20 °C
% Org. carbon:
3.3
Type:
Kd
Remarks:
Soil 4
Value:
20
Temp.:
20 °C
% Org. carbon:
1.4
Type:
Kd
Remarks:
Soil 5
Value:
75
Temp.:
20 °C
% Org. carbon:
4.4
Type:
Kd
Remarks:
Soil (average of 5 Soils)
Value:
47
Temp.:
20 °C
% Org. carbon:
3
Type:
Kd
Remarks:
Sediment
Value:
23
Temp.:
20 °C
% Org. carbon:
0.3

Results: Batch equilibrium or other method

Details on results (Batch equilibrium method):
PRELIMINARY TEST
- Weighed soil: 1.8-2.0 g
- Initial test substance concentration: 50 µg/cm³

Any other information on results incl. tables

Measurements and results for Kd and Koc values (one concentration of 50 mg/L test substance) in the different soils.

Soil No.

Initial concentration (µg/cm³)

Kd (cm³/g)

Koc (cm³/g)

1

50

50.09

1522.5

2

50

56.13

2348.5

3

50

35.45

1067.8

4

50

19.76

1452.9

5

50

74.85

1689.6

Sediment

50

23.19

7480.6

% Desorption and Adsorption

Soil No.

Initial concentration (µg/cm³)

% Adsorption

% Desorption

1

50

65

0

2

50

68

0

3

50

58

0

4

50

43

0

5

50

75

0

Sediment

50

48

0

FREUNDLICH Coefficients (adsorption and desorption)

Soil No.

Initial concentration (µg/cm³)

FREUNDLICH Adsorption Coefficient log KF(ads)

FREUNDLICH Adsorption Coefficient log KF(des)

1

20 to 100

0.87

n.d.

2

20 to 100

2.5

n.d.

3

20 to 100

1.13

n.d.

4

20 to 100

1.03

n.d.

5

20 to 100

2.08

2.7

Sediment

20 to 100

0.99

n.d.

Applicant's summary and conclusion

Conclusions:
Sorption process of test item on soil can be regarded as the sum of two processes, an irreversible and a reversible one. The reversible one is measured in the desorption step. The sorption process is completely reversible, if the measured adsortion coefficient is equal to the measured description coefficient.

The test item showed a moderate to higher adsorption tendency under test conditions to the five soils and sediment tested. The organic carbon normalized distribution coefficient (Koc) and FREUNDLICH adsorption coefficient (KFoc) do not correlate with the organic content of the soil, but suggest that other mechanisms were involved in the adsorption of the test item to soil (e.g. interactions with the inorganic matter of the soil). In addition, the desorption was verly low. Therefore, the test item can be classified as being immobile in soil.
Executive summary:

Hostapur SAS 60 showed a moderate to higher adsorption tendency under test conditions to the five soils and sediment tested. The organic carbon normalized distribution coefficient (Koc) and FREUNDLICH adsorption coefficient (KFoc) do not correlate with the organic content of the soil , but suggest that other mechanisms were involved in the adsorption of Hostapur SAS to soil (e.g. interactions with the inorganic matter of the soil). In addition, the desorption was very low. therefore, Hostapur SAS 60 can be classified as being immobile in soil.