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adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
supporting study
1 (reliable without restriction)

Data source

Reference Type:
study report

Materials and methods

Test guideline
according to guideline
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
GLP compliance:
Type of method:
batch equilibrium method

Test material

Constituent 1
Chemical structure
Reference substance name:
Pyridine-2-thiol 1-oxide, sodium salt
EC Number:
EC Name:
Pyridine-2-thiol 1-oxide, sodium salt
Cas Number:
Molecular formula:
sodium (1-oxo-1lambda5-pyridin-2-yl)sulfanide
Details on test material:
- Lot/batch No.: SB-D010010

Study design

Test temperature:
21 to 22 °C

HPLC method

Details on study design: HPLC method:
HPLC with UV-detector

Batch equilibrium or other method

Details on matrix:
Five soils were collected from sites in Austria and Germany.
Soil Clay (%) Organic C (%) pH
Silty loam 23.1 2.4 7.5
Clay loam 30.1 3.5 5.3
Loam 16.9 3.1 7.1
Clay 69.0 2.6 8.3
Sand 2.2 0.51 5.5
The soils were air dried and passed through a 2 mm sieve.
Details on test conditions:
0.01 M CaCl2 is added to the soils in polyethylene tubes. After equilibration, aliquots of a stock solution of the test substance in 0.01 M CaCl2 are added. Agitation of the mixtures for various times. Analysis of the supernatant.
All experiments were performed in duplicate.

Results and discussion

Results: Batch equilibrium or other method

Adsorption and desorption constants:
Adsorption: Soil Kd Koc
Silty loam 31 1300
Clay loam 2100 59500
Loam 74 2400
Clay 12 460
Sand 47 9100
Desorption: Derived mean desorption distribution coefficients, after 4 h:
Soil Kd Koc
Silty loam 290 12000
Clay loam 5800 165000
Loam 440 14000
Clay 96 3650
Sand 1600 310000
Recovery of test material:
Mass balance: Recovery of 100 % for soil-less controls. Recoveries of 14 to 83 % for the test samples.
Concentration of test substance at end of adsorption equilibration period:
The test substance was adsorbed to more than 50 % to all the soils tested except for the clay soil after 24 h. For the clay soil, ca. 30 % were adsorbed after 24 h. Highest adsorption (90 %) was observed for the clay loam. The sorption behaviour was related to the pH of the soil. Soils with low pH showed higher sorptions than neutral or basic soils.
Equilibrium was reached within 24 h.
Concentration of test substance at end of desorption equilibration period:
The equilibrium was rapidly attained within 4 hours, only for clay soil it was reached after 7 h.
Desorption was < 3.1 % for clay loam and sand soils, <10 % for silty loam and loam soil and <31 % for clay soil.
Details on results (Batch equilibrium method):
Very high sorption was obtained for the acidic soils, high sorption for the neutral soils and moderate sorption for the basic soil. However Kf sorption values >90 together with Kf desorption values >190 for all investigated solis suggest that leaching potential of the test substance is low in soils used in the study.
Normalising the Kd and Kf values for organic carbon (Koc), results in a greater range of values than the original Kd and Kf values for the investigated soils. In addition the observed sorption behaviour suggest that sorption and desorption is more dependent on pH of the soil than the texture and organic carbon content. Therefore, the Kd and Kf values may be more appropriate for estimating the partitioning of the test substance in soil than the Koc values.

Any other information on results incl. tables

Mean adsorption distribution coefficients:

               Soil               Kd         Koc
               Silty loam             31          1300
               Clay loam            2100      59500
             74          2400
             12          460
             47          9100

Mean Freundlichs sorption distribution coefficients:

       Soil                                      Kf                             Koc
       Silty loam                        260                         11000
       Clay loam                     1800                         51000
       Loam                                340                         11000
       Clay                                    91                           3500
       Sand                                 410                         80000

Mean desorption distribution coefficients, after 4 h:

       Soil                                     Kd                             Koc
       Silty loam                        290                         12000
       Clay loam                     5800                       165000
       Loam                                440                         14000
       Clay                                    96                           3650
       Sand                               1600                       310000

Mean Freundlichs desorption distribution coefficients:

       Soil                                      Kf                             Koc
       Silty loam                        390                         16000
       Clay loam                     3800                       110000
       Loam                                550                         18000
       Clay                                  190                           7300
       Sand                               1400                       270000

Applicant's summary and conclusion

Very high sorption was obtained for the acidic soils, high sorption for the neutral soils and moderate sorption for the basic soil. The information contained within this robust summary document comes from studies which are in the ownership of Arch Chemicals Inc. and which are protected in several regions globally. This information may not be used for any purpose other than in support of the Chemical safety Report submitted by Arch Chemicals Inc. under Regulation EC 1907/2006.