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Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption, other
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1997-09-16 - 1997-09-30
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Qualifier:
according to
Guideline:
other: no guideline available
Principles of method if other than guideline:
The extent of adsorption of chemical onto sediment or soil is measured by equilibrating chemicals aqueous solutions with different quantities of sediment or soil. After steady-state is reached, the distribution of chemical between the water phase and the solid phase is quantitatively measured by a suitable analytical method.
GLP compliance:
no
Type of method:
batch equilibrium method
Media:
soil
Radiolabelling:
yes
Test temperature:
25.0 °C
Analytical monitoring:
not specified
Details on sampling:
see 'Any other information on materials and methods incl. tables'
Details on matrix:
see 'Any other information on materials and methods incl. tables'
Details on test conditions:
see 'Any other information on materials and methods incl. tables'
Remarks:
see 'Any other information on materials and methods incl. tables'
Remarks:
see 'Any other information on materials and methods incl. tables'
Computational methods:
see 'Any other information on materials and methods incl. tables'
Sample No.:
#1
Type:
Koc
Value:
53.4 dimensionless
Sample No.:
#2
Type:
Koc
Value:
11.9 dimensionless
Sample No.:
#3
Type:
Koc
Value:
8.3 dimensionless
Adsorption and desorption constants:
see 'Any other information on results incl. tables'
Recovery of test material:
not specified
Concentration of test substance at end of adsorption equilibration period:
not specified
Concentration of test substance at end of desorption equilibration period:
not specified
Sample no.:
#1
% Adsorption:
93
Sample no.:
#2
% Adsorption:
70
Sample no.:
#3
% Adsorption:
60
Transformation products:
not specified
Details on results (Batch equilibrium method):
see 'Any other information on results incl. tables'
Statistics:
see 'Any other information on results incl. tables'

Table 2 shows the results of radioactivity from samples for the adsorption/desorption experiment with GH, LR and LE soils. Table 3 shows average values for the equilibrium concentrations (Ce) in solutions, and Table 4 shows the average values for the total amount of test substance in these soils. Table 5 shows the equations of Freundlich isotherms, coefficients of adsorption (K) and coefficient for soil organic matter (Koc). Table 6 shows the adsorption/desorption classification of chemical, according to MHM/SEMA.

According to the Table 4, the total amount of the test substance ferbam adsorbed on GH soil was about 93%. On LR soil was about 70%, and on LE soil 60%. The coefficients of adsorption and desorption from GH soil were 53.4 and 257.4, from LR soil were 11.9 and 19.7, and from LE soil these coefficients were 8.3 and 42.6, respectively.

Table 2: Results of radioactivity in disintegration per minute (dpm) in the experiment using 5 concentrations of test substance and standard on GH, LR and LE soils (2 replicates).

Solution
(ug / mL)
GH LR LE Standard
Ads. Des. Ads. Des. Ads. Des.
0,5 2859 1057 10385 3040 15980 4845 62238
2887 977 9395 2436 15988 4711
1,0 2903 1011 8402 2479 14625 4610 58055
2931 1046 8548 2520 14726 4604
5,0 2895 1181 10084 2333 17438 3501 56301
2906 1564 11400 2333 18021 3773
10,0 3441 1394 26963 2930 29339 4535 56958
3202 1321 25788 2994 29371 4579
20,0 8187 1744 35584 5553 40386 5583 57128
7524 1497 35396 5576 38911 5744

Table 3: Equilibrium concentration in the solution (Ce) using 5 concentrations of test substance in GH, LR and LE soil (2 replicates)

Solution
(ug / mL)
GH Ce (ug /mL)
LR
LE
Ads Des Ads Des Ads Des
0,5 0,023 0,006 0,079 0,013 0,128 0,027
1,0 0,050 0,011 0,146 0,026 0,253 0,057
5,0 0,258 0,088 0,954 0,100 1,575 0,198
10,0 0,583 0,162 4,631 0,002 5,154 0,375
20,0 2,750 0,240 12,425 0,538 13,881 0,860

Table 4: Total amount of test substance adsorbed and desorbed on GH, LR and LE soils (means of 2 replicates) using 5 concentrations of test substance.

Concentration
Solution
(ug / mL)
(ug / g)
GH LR LE
Ads. Des. Ads. Des. Ads. Des.
0,5 2,38 0,03 2,10 0,06 1,86 0,13
1,0 4,75 0,06 4,27 0,13 3,74 0,29
5,0 23,71 0,44 20,23 0,50 17,13 0,99
10,0 47,08 0,81 26,85 0,01 24,23 1,87
20,0 86,25 1,20 37,88 2,69 30,60 4,30

Table 5: Freundlich isotherm equations and K values for GH, LR and LE soils

Equations K
(ug / g)
Koc R2*
GH soil
Adsorption log x / m = log 53,43 + 0,784 log Ce 53,4 1094 97,0
Desorption log x / m = log 257,4 + 0,909 log Ce 257,4 99,1
LR soil
Adsorption log x / m = log 11,89 + 0,558 log Ce 11,9 672 92,4
Desorption log x / m = log 19,74 + 0,171 log Ce 19,7 85,3
LE soil
Adsorption log x / m = log 8,33 + 0,608 log Ce 8,3 678 94,2
Desorption log x / m = log 42,55 + 0,846 log Ce 42,6 94,2
* Correlation coefficient

Table 6: Adsorption/Desorption classification of test substance according to MHM/SEMA, 1990

Ka values Adsorption
0 - 5 low
> 5 - 15 medium
> 15 - 80 high
> 80 very high
Validity criteria fulfilled:
not specified
Conclusions:
The total amount of the test substance ferbam adsorbed on GH soil was about 93%. On LR soil was about 70%, and on LE soil 60%. The coefficients of adsorption and desorption from GH soil were 53.4 and 257.4, from LR soil were 11.9 and 19.7, and from LE soil these coefficients were 8.3 and 42.6, respectively.
Executive summary:

This study was conducted to determine the adsorption and desorption characteristics of ferbam on LE {Typic Hapludox), GH {Cumulic Humaquept) and LR (Rhodic Hapludox) soils.

The extent of adsorption of chemical onto sediment or soil is measured by equilibrating chemicals aqueous solutions with différents quantities of sediment or soil. After steady-state is reached, the distribution of chemical between the water phase and the solid phase is quantitatively measured by a suitable analytical method.

The following concentrations of active ingredient were used: 0.5, 1.0, 5.0, 10.0 and 20.0 ug of ferbam/mL and 0.01 uCi/mL of radioactivity. The assay was carried out with two replicates in centrifuge tubes containing 1.0g of soil and 5.0 mL of treating solutions, that were agitated and centrifuged. Aliquots of the supernatant were pipetted and analyzed using the Liquid Scintillation Analyzer to quantify the amount of test compound remaining in the solution. The amount of adsorbed product was then calculated. To quantify the desorbed product, the supernatant solution was completely drained, and 5.0 mL of 0.01M CaCl2 was added. The tubes were agitated, centrifuged, sampled and analyzed as above mentioned.

According to the results, the coefficients of adsorption from GH, LR and LE soils were 53.4, 11.9 and 8.3, respectively.

Description of key information

Test procedure was conducted in accordance with generally accepted scientific standards and described in sufficient detail. The extent of adsorption of chemical onto sediment or soil is measured by equilibrating chemicals aqueous solutions with differents quantities of sediment or soil. After steady-state is reached, the distribution of chemical between the water phase and the solid phase is quantitatively measured by a suitable analytical method.

The total amount of the test substance ferbam adsorbed on GH soil was about 93%. On LR soil was about 70%, and on LE soil 60%. The coefficients of adsorption and desorption from GH soil were 53.4 and 257.4, from LR soil were 11.9 and 19.7, and from LE soil these coefficients were 8.3 and 42.6, respectively.

Key value for chemical safety assessment

Koc at 20 °C:
1 094

Additional information

Key: da Silva, 1997

This study was conducted to determine the adsorption and desorption characteristics of ferbam on LE {Typic Hapludox), GH {Cumulic Humaquept) and LR (Rhodic Hapludox) soils.

The extent of adsorption of chemical onto sediment or soil is measured by equilibrating chemicals aqueous solutions with différents quantities of sediment or soil. After steady-state is reached, the distribution of chemical between the water phase and the solid phase is quantitatively measured by a suitable analytical method.

The following concentrations of active ingredient were used: 0.5, 1.0, 5.0, 10.0 and 20.0 ug of ferbam/mL and 0.01 uCi/mL of radioactivity. The assay was carried out with two replicates in centrifuge tubes containing 1.0g of soil and 5.0 mL of treating solutions, that were agitated and centrifuged. Aliquots of the supernatant were pipetted and analyzed using the Liquid Scintillation Analyzer to quantify the amount of test compound remaining in the solution. The amount of adsorbed product was then calculated. To quantify the desorbed product, the supernatant solution was completely drained, and 5.0 mL of 0.01M CaCl2 was added. The tubes were agitated, centrifuged, sampled and analyzed as above mentioned.

According to the results, the coefficients of adsorption from GH, LR and LE soils were 53.4, 11.9 and 8.3, respectively.

Supporting information: Warren, 1987

Aqueous solutions of 14C-Ferbam were equilibrated with four soil types and the adsorption coefficients and adsorptions constants were determined. Liquid scintillation counting analysis was employed to measure test material concentrations in the aqueous phase.

The results are summarized below:

  Soil Type     % Organic Carbon    Adsorption     Desorption   
 Kd  Koc  Kc  Koc

 #1

Ahapulgus Sandy loam

 0.826  3.57  432  20.40  2470

 #2

Leon Sand

 0.913  20.15  2207  98.87  10829

 #3

Crittendon Silt Loam

 1.30  14.9  1146  39.00  3000

 #4

Clay Loam

 2.43  22.9  942  53.26  2192