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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
The study was conducted betwen 15 May 2018 and 19 July 2018.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Reliability 1 is assigned because the study was conducted according to OECD TG 106 in compliance with GLP, without deviations that influence the quality of the results.
Qualifier:
according to guideline
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Deviations:
no
GLP compliance:
yes
Type of method:
batch equilibrium method
Media:
other: soil-adsorption reference data
Specific details on test material used for the study:
Identification: FRET 15-0735
Physical state / Appearance: clear colorless liquid
Storage conditions: room temperature in the dark
Radiolabelling:
no
Test temperature:
25°C ± 2°C
Analytical monitoring:
yes
Remarks:
high performance liquid chromatography (HPLC)
Details on sampling:
See "Test conditions" section
Matrix no.:
#2
Matrix type:
sandy clay loam
% Org. carbon:
2.61
pH:
7.3
CEC:
19.5 other: Cmol+/kg
Matrix no.:
#3
Matrix type:
silt loam
% Org. carbon:
4.38
pH:
5.3
CEC:
15 other: Cmol+/kg
Matrix no.:
#4
Matrix type:
silt loam
% Org. carbon:
3.84
pH:
4.9
CEC:
12.4 other: Cmol+/kg
Matrix no.:
#5
Matrix type:
loamy sand
% Org. carbon:
1.12
pH:
5.2
CEC:
6.7 other: Cmol+/kg
Matrix no.:
#7
Matrix type:
sandy loam
% Org. carbon:
25.05
pH:
3.2
CEC:
38.8 other: Cmol+/k g
Details on matrix:
All soils are stored air dried, in the dark, at ambient temperature. Organic carbon content, CEC and pH are re-analyzed at least every 3 years. With the exception of the moisture contents, characterization of the soils used was performed by LUFA Speyer, Germany, under the GLP Compliant study BP 05/18, a copy of which has been retained with the raw data package for this study. The moisture content data was generated by Envigo, specific to this study.
Details on test conditions:
Identification of Optimal Soil to Solution Ratio
Method
Three contrasting soil types were initially investigated using a range of nominal soil to solution ratios, in order to identify the ratio at which the percentage of test item adsorbed was optimized for the determination of the distribution coefficient (Kd) and the organic carbon normalized adsorption coefficient (Koc) of the test item.
Testing used a direct method, designed to be compatible with Method 106 of the OECD Guidelines for Testing of Chemicals, 21 January 2000.

Procedure
Aliquots of soil and 0.01 M calcium chloride solution (see the following table) were taken in FEP/ETFE (fluorinated ethylene propylene/ethylene tetrafluoroethylene) centrifuge tubes. Aliquots of 0.01 M calcium chloride solution required for soil-less controls and solvent only blanks were also taken in these test vessels.

The resulting mixtures were pre-equilibrated by shaking at 25 ± 2 °C overnight prior to addition of the test item.

Preparation of stock solution
An aliquot of test item (0.1006 g) was dissolved in 10 mL of acetonitrile. The stock solution was such that a nominal concentration of 10 mg/L was obtained when 25 µL was spiked into samples containing 25 mL of aqueous solution.

Addition of test item into samples
Stock solution (25 µL) was added to all samples and soil-less controls.
Each control, sample and blank was then shaken for an adsorption period of 24-hours at 25 ± 2 ºC, in the dark.
After a 24-hour adsorption period, the samples, controls and blanks were centrifuged at 6000 rpm for 15 minutes and the supernatants isolated for analysis.
The pH of all solutions was recorded.

Determination of Adsorption Equilibration Time
Testing was continued using the identified optimum soil to solution ratio for each soil type to determine the adsorption equilibration time required until no further significant adsorption of the test item occurred. Testing was carried out using an indirect, parallel method.

Procedure
Aliquots of soil and 0.01 M calcium chloride solution (see following table) were taken in FEP/ETFE (fluorinated ethylene propylene/ethylene tetrafluoroethylene) centrifuge tubes. Aliquots of 0.01 M calcium chloride solution required for soil-less controls and solvent only blanks were also taken in these test vessels.
Due to the capacity of necessary apparatus, testing was split into two groups of soil type 2, soil type 3 and soil type 5, and then soil type 4 and soil type 7. For this reason, separate control and solvent only blank preparations are presented within this section. Control solutions A to C and solvent only blank A and B were prepared and analyzed with the soil type 2, soil type 3 and soil type 5 testing. Control solutions D to F and solvent only blank C and D were prepared and analyzed with soil type 4 and soil type 7 testing.

The resulting mixtures were pre-equilibrated by shaking at 25 ± 2 ºC overnight prior to addition of the test item.

Preparation of stock solution for evaluation of soil type 2, soil type 3 and soil type 5
An aliquot of test item (0.08122 g) was dissolved in 200 mL of 0.01 M calcium chloride solution. An aliquot of this solution was then further diluted by a factor of 2.5 using 0.01 M calcium chloride solution to prepare the stock solution. The stock solution was such that a nominal concentration of 10 mg/L was obtained when 1.0 mL was spiked into samples containing 15 mL of aqueous solution.

Preparation of stock solution for evaluation of soil type 4 and soil type 7
An aliquot of test item (0.08301 g) was dissolved in 200 mL of 0.01 M calcium chloride solution. An aliquot of this solution was then further diluted by a factor of 2.5 using 0.01 M calcium chloride solution to prepare the stock solution. The stock solution was such that a nominal concentration of 10 mg/L was obtained when 1.0 mL was spiked into samples containing 15 mL of aqueous solution.

Addition of test item into samples
Relevant stock solution (1.0 mL) was added to all samples and soil-less controls.
An aliquot (1.0 mL) of 0.01 M calcium chloride solution was added to all soil only blanks and the solvent only blanks.
Each sample was then shaken for its respective adsorption period at 25 ± 2 ºC, in the dark.
Solvent blanks and soil only blanks were removed with the 48-hour adsorption equilibrium timepoint samples.
After the relevant adsorption period, the samples, controls and blanks were centrifuged at 6000 rpm for 15 minutes and the supernatants isolated for analysis.
The pH of all solutions was recorded.

Analysis of solutions
As for “Identification of Optimal Soil to Solution Ratio”.

Determination of Desorption Equilibration Time
Method
The desorption equilibration time required until no further significant desorption of the test item from the soil phase occurred was determined. A 48-hour adsorption equilibration period was previously determined to be sufficient for all soil types.
Testing was performed using an indirect, parallel method.

Procedure
Aliquots of soil and 0.01 M calcium chloride solution (see following table) were taken in FEP/ETFE (fluorinated ethylene propylene/ethylene tetrafluoroethylene) centrifuge tubes. Aliquots of 0.01 M calcium chloride solution required for soil-less controls and solvent only blanks were also taken in these test vessels.
Due to the capacity of necessary apparatus, testing was split into two groups of soil type 2, soil type 3 and soil type 5, and then soil type 4 and soil type 7. For this reason, separate control and solvent only blank preparations are presented within this section. Control solutions A to C and solvent only blank A and B were prepared and analyzed with the soil type 2, soil type 3 and soil type 5 testing. Control solutions D to F and solvent only blank C and D were prepared and analyzed with soil type 4 and soil type 7 testing.
The resulting mixtures were pre-equilibrated by shaking at 25 ± 2 ºC overnight, prior to addition of the test item.

Preparation of stock solution for evaluation of soil type 2, soil type 3 and soil type 5
An aliquot of test item (0.08141 g) was dissolved in 200 mL of 0.01 M calcium chloride solution. An aliquot of this solution was then further diluted by a factor of 2.5 using 0.01 M calcium chloride solution to prepare the stock solution. The stock solution was such that a nominal concentration of 10 mg/L was obtained when 1.0 mL was spiked into samples containing 15 mL of aqueous solution.

Preparation of stock solution for evaluation of soil type 4 and soil type 7
An aliquot of test item (0.08180 g) was dissolved in 200 mL of 0.01 M calcium chloride solution. An aliquot of this solution was then further diluted by a factor of 2.5 using 0.01 M calcium chloride solution to prepare the stock solution. The stock solution was such that a nominal concentration of 10 mg/L was obtained when 1.0 mL was spiked into samples containing 15 mL of aqueous solution.

Addition of test item into samples
Relevant stock solution (1.0 mL) was added to all samples and soil-less controls.
An aliquot (1.0 mL) of 0.01 M calcium chloride solution was added to all soil only blanks and the solvent only blanks.

Adsorption step
Each sample was shaken at 25 ± 2 ºC, in the dark, for 48-hours; the adsorption equilibration period.

Analysis at adsorption equilibrium
After the 48-hour adsorption period, the tubes were centrifuged at 6000 rpm for a minimum of 15 minutes and the maximum possible volume of aqueous phase removed into a tared vessel. The mass of supernatant recovered was recorded in each case.
The pH of all solutions was recorded.
The concentration of test item in the adsorption stage sample supernatants was determined by high performance liquid chromatography (HPLC).

Analysis
As for “Identification of Optimal Soil to Solution Ratio”.

Desorption step
The volume of aqueous phase removed from all samples and soil only blanks was replaced with an approximately equal weight (volume) of 0.01 M calcium chloride solution and the test vessels returned to shaking at 25 ± 2 ºC, in the dark, i.e. the desorption period. On completion of the required desorption equilibration period, the samples were removed for analysis.

Analysis following desorption step
On completion of the relevant desorption period, each soil sample was centrifuged at 6000 rpm for 15 minutes and an aliquot of supernatant diluted for analysis, as detailed for the adsorption stage.
All soil only blanks were removed with the 48-hour desorption period samples. Each blank was centrifuged and diluted for analysis as detailed for the samples.
The pH of all solutions was recorded.

Determination of Adsorption Isotherms
Method
The Freundlich adsorption isotherms were determined evaluating five test item concentrations, utilizing the optimal soil to solution ratio and adsorption equilibrium time previously identified.
The concentrations selected were 1.0 mg/L, 3.0 mg/L, 10 mg/l, 30 mg/L and 100 mg/L. The rationale for the selection of these five concentrations was the guideline requirement of evaluating a range covering two magnitudes of concentration. In addition, the concentration range selected was significantly below half the known water solubility of the test item, which was the maximum concentration permitted by the guideline, whilst remaining within the working range of the analytical method. Finally the spacing of the five concentrations was exponential, as a log transformation is performed on the data during the calculation of the isotherms, thus giving an even distribution of data points for the final correlation plots.
Analytical data for a nominal test item concentration of 10 mg/L, generated during the adsorption step of the desorption kinetics testing (24 hour desorption period, duplicate samples), has been transcribed from Section 4.3 of this report, to allow calculation of the Freundlich adsorption coefficients.

Procedure
Aliquots of soil and 0.01 M calcium chloride solution (see following table) were taken in FEP/ETFE (fluorinated ethylene propylene/ethylene tetrafluoroethylene) centrifuge tubes. Aliquots of 0.01 M calcium chloride solution (15 mL) required for triplicate soil-less controls and duplicate solvent only blanks were also taken in these test vessels.
The analytical procedure was performed at nominal concentrations of 1.0 mg/L and 3.0 mg/L, and 30 mg/L and 100 mg/L separately, due to capacity of the necessary experimental apparatus. Therefore soil only blanks and solvent only blanks were prepared for both determinations and two sets of data are presented in the report. Blanks A and B are as analyzed with the 1.0 mg/L and 3.0 mg/L determination, and blanks C and D are as analyzed with 30 mg/L and 100 mg/L determination.
The resulting mixtures were pre-equilibrated by shaking at 25 ± 2 ºC overnight prior to addition of the test item.

Preparation of stock solution (1.0 mg/L nominal fortification concentration)
An aliquot of test item (0.08448 g) was dissolved in 200 mL of 0.01 M calcium chloride solution. An aliquot of this solution was then further diluted by a factor of 25 using 0.01 M calcium chloride solution prior to use, to give a nominal concentration of 16 mg/L.
The stock solution was such that a nominal concentration of 1.0 mg/L was obtained when 1.0 mL was spiked into samples containing 15 mL of aqueous solution.

Preparation of stock solution (3.0 mg/L nominal fortification concentration)
An aliquot of test item (0.08448 g) was dissolved in 200 mL of 0.01 M calcium chloride solution. An aliquot of this solution was then further diluted by a factor of 8.3 using 0.01 M calcium chloride solution prior to use, to give a nominal concentration of 48 mg/L.
The stock solution was such that a nominal concentration of 3.0 mg/L was obtained when 1.0 mL was spiked into samples containing 15 mL of aqueous solution.

Preparation of stock solution (30 mg/L nominal fortification concentration)
An aliquot of test item (1.0035 g) was dissolved in 10 mL of acetonitrile. This solution was then diluted by a factor of 3.3 with acetonitrile prior to use, to give a nominal concentration of 3.00 x 10^4 mg/L.
The stock solution was such that a nominal concentration of 30 mg/L was obtained when 15 µL was spiked into samples containing 15 mL of aqueous solution.

Preparation of stock solution (100 mg/L nominal fortification concentration)
An aliquot of test item (1.0035 g) was dissolved in 10 mL of acetonitrile, to give a nominal concentration of 1.00 x 10^5 mg/L.
The stock solution was such that a nominal concentration of 100 mg/L was obtained when 15 µL was spiked into samples containing 15 mL of aqueous solution.

Addition of test item into samples
Relevant stock solution (1.0 mL or 15 µL, as indicated) was added to all samples and soil-less controls.
An aliquot (1.0 mL) of 0.01 M calcium chloride solution was added to all soil only and solvent only blanks for testing at the 1.0 mg/L and 3.0 mg/L nominal fortification concentrations. No further addition was performed to the soil only and solvent only blanks for testing at the 30 mg/L and 100 mg/L nominal fortification concentrations.

Adsorption step
Each sample was shaken at 25 ± 2 ºC, in the dark, for 48-hours; the adsorption equilibration period.

Analysis at adsorption equilibrium
After the 48-hour adsorption period, the samples and soil blanks were centrifuged at 6000 rpm for a minimum of 15 minutes and the maximum possible volume of aqueous phase removed to a tared vessel. The mass of supernatant recovered was recorded in each case.

For testing at 1.0 mg/L and 3.0 mg/L nominal fortification concentrations, aliquots of each supernatant, the control solutions and the solvent only blanks were diluted by a factor of 2 with methanol for analysis.
For testing at the 30 mg/L nominal fortification concentrations, aliquots of each supernatant, the control solutions and the solvent only blanks were diluted by a factor of 10 with a diluent of methanol: 0.01 M calcium chloride solution (50:50 v/v) for analysis. The soil only and solvent blanks were also relevant to the 100 mg/L nominal fortification concentration.
For testing at the 100 mg/L nominal fortification concentration, aliquots of each sample supernatant and the control solutions were diluted by a factor of 20 with a diluent of methanol: 0.01 M calcium chloride solution (50:50 v/v) for analysis.
The pH of all solutions was recorded.

Determination of Desorption Isotherms
Method
The Freundlich desorption isotherms were determined as a continuation of the adsorption isotherm testing.
Analytical data for a nominal test item concentration of 10 mg/L, generated during the adsorption step of the desorption kinetics testing (24 hour desorption period duplicate samples) to allow calculation of the Freundlich desorption coefficients.

Procedure
On completion of the adsorption equilibrium sampling the volume of supernatant removed was replaced with an approximately equal volume of 0.01 M calcium chloride solution.
Each sample was then shaken at 25 ± 2 ºC, in the dark, for a desorption equilibrium period of 24-hours.
After the 24-hour desorption period, the samples and soil blanks were centrifuged at 6000 rpm for 15 minutes and the supernatants sampled for analysis.
For testing at 1.0 mg/L and 3.0 mg/L nominal fortification concentrations, aliquots of each supernatant were diluted by a factor of 2 with methanol for analysis.
For testing at the 30 mg/L nominal fortification concentrations, aliquots of each supernatant were diluted by a factor of 10 with a diluent of methanol: 0.01 M calcium chloride solution (50:50 v/v) for analysis. The soil only blanks were also relevant to the 100 mg/L nominal fortification concentration.
For testing at the 100 mg/L nominal fortification concentration, aliquots of each supernatant were diluted by a factor of 20 with a diluent of methanol: 0.01 M calcium chloride solution (50:50 v/v) for analysis.
The pH of all solutions was recorded.
Type:
log Koc
Value:
>= 1.51 - <= 2.49 dimensionless
Temp.:
25 °C
Adsorption and desorption constants:
Adsorption:
The distribution coefficient (Kd) and the organic carbon normalized adsorption coefficient (Koc) at adsorption equilibrium were determined for five different soil types, at 25 ± 2 ºC.
Overall Kd range: 0.439 to 77.8 cm3/g
Overall Koc range: 32.4 to 310 cm3/g
log10 Koc range: 1.51 to 2.49

Desorption:
The apparent desorption coefficient (Kdes) and the organic carbon normalized apparent desorption coefficient (Kdes (oc)) at desorption equilibrium were determined for five different soil types at 25 ± 2 ºC.
Overall Kdes range: 2.10 to 106 cm^3/g
Overall Kdes (oc) range: 105 to 422 cm^3/g
log10 Kdes (oc) range: 2.02 to 2.62
Transformation products:
not measured
Details on results (Batch equilibrium method):
See "Any other information on results"

Identification of Optimal Soil to Solution Ratio

The soil-less control recoveries on completion of the adsorption equilibration period, calculated with respect to the theoretical dosed concentration, are shown in the following table:

 

Solution

Theoretical Dosed Concentration (mg/L)

Analyzed Concentration (mg/L)

Mean Analyzed Concentration (mg/L)

Recovery
(%)

Soil-less Control A

10.1

11.1

11.0

110

Soil-less Control B

11.1

111

Soil-less Control C

10.8

108

 

The concentration of test item analyzed in each sample solution, the pH of each solution and the percentage of test item adsorbed with respect to the analytically proven dosed concentration (11.0 mg/L, from the mean control solution concentration) are shown in the following table:

 

Solution

Concentration (mg/L)

Solution pH

Percentage Adsorption (%)

Mean Percentage Adsorption (%)

Soil Type 2,1:2Ratio, Sample A

6.38

6.9

42.1

42.9

Soil Type 2,1:2Ratio, Sample B

6.21

6.9

43.6

Soil Type 2, 1:10 Ratio Sample A

9.62

7.0

12.7

13.7

Soil Type 2, 1:10 Ratio, Sample B

9.39

6.9

14.8

Soil Type 2, 1:25 Ratio Sample A

10.5

7.1

4.46

4.67

Soil Type 2, 1:25 Ratio, Sample B

10.5

7.1

4.88

Soil Type 5,1:2Ratio, Sample A

9.55

6.0

13.3

13.1 

Soil Type 5,1:2Ratio, Sample B

9.60

6.0

12.9

Soil Type 5, 1:10 Ratio Sample A

11.0

6.2

<2.0

<2.0

Soil Type 5, 1:10 Ratio, Sample B

10.9

6.2

<2.0

Soil Type 5, 1:25 Ratio Sample A

10.8

6.2

<2.0

<2.0

Soil Type 5, 1:25 Ratio, Sample B

11.2

6.2

<2.0

Soil Type 7,1:10Ratio, Sample A

1.52

3.1

86.2

86.4 

Soil Type 7,1:10Ratio, Sample B

1.48

3.2

86.6

Soil Type 7, 1:25 Ratio Sample A

3.47

3.2

68.5

69.3 

Soil Type 7, 1:25 Ratio, Sample B

3.29

3.1

70.1

Soil Type 7, 1:100 Ratio Sample A

7.59

3.4

31.1

32.8

Soil Type 7, 1:100 Ratio, Sample B

7.22

3.4

34.5

The pH of the control and blank solutions are shown in the following table:

 

Solution

pH

Soil Type 2, Soil Only Blank A

6.8

Soil Type 2, Soil Only Blank B

6.8

Soil Type 5, Soil Only Blank A

6.0

Soil Type 5, Soil Only Blank B

6.1

Soil Type 7, Soil Only Blank A

3.1

Soil Type 7, Soil Only Blank B

3.1

 

Solution

pH

Solvent Only Blank A

6.9

Solvent Only Blank B

7.1

Soil-less Control A

7.2

Soil-less Control B

7.1

Soil-less Control C

7.2

 

Determination of Adsorption Equilibration Time

The soil-less control recoveries on completion of each adsorption equilibration period, calculated with respect to the theoretical dosed concentration, are shown in the following tables:

 

Testing of Soil Type 2, Soil Type 3 and Soil Type 5 

Solution

Theoretical Dosed Concentration (mg/L)

Analyzed Concentration (mg/L)

Mean Analyzed Concentration (mg/L)

Recovery
(%)

Control A at 2-hour Timepoint

10.2

10.1

 

10.3

 

99.3

Control B at 2-hour Timepoint

10.3

101.4

Control C at 2-hour Timepoint

10.7

105.2

Control A at 5-hour Timepoint

10.2

 

10.3

 

100.1

Control B at 5-hour Timepoint

10.2

100.6

Control C at 5-hour Timepoint

10.7

105.1

Control A at 24-hour Timepoint

10.0

 

10.3

 

98.7

Control B at 24-hour Timepoint

10.2

100.7

Control C at 24-hour Timepoint

10.5

103.8

Control A at 48-hour Timepoint

10.1

 

10.3

 

99.1

Control B at 48-hour Timepoint

10.2

100.9

Control C at 48-hour Timepoint

10.6

104.8

 

Testing of Soil Type 4 and Soil Type 7 

Solution

Theoretical Dosed Concentration (mg/L)

Analyzed Concentration (mg/L)

Mean Analyzed Concentration (mg/L)

Recovery
(%)

Control D at 2-hour Timepoint

10.4

10.6

 

10.6

 

102.1

Control E at 2-hour Timepoint

10.5

100.7

Control F at 2-hour Timepoint

10.8

104.5

Control D at 5-hour Timepoint

10.5

 

10.6

 

101.4

Control E at 5-hour Timepoint

10.5

100.9

Control F at 5-hour Timepoint

10.7

103.3

Control D at 24-hour Timepoint

10.4

 

10.4

 

100.3

Control E at 24-hour Timepoint

10.3

99.4

Control F at 24-hour Timepoint

10.6

102.0

Control D at 48-hour Timepoint

10.3

 

10.5

 

99.6

Control E at 48-hour Timepoint

10.4

100.5

Control F at 48-hour Timepoint

10.8

104.3

 

The concentration (mg/L) of test item analyzed in each sample, the solution pH and the percentage of test item adsorbed with respect to the relevant mean analyzed control concentration are shown in the following tables:

 

Soil Type 2 

Solution

Concentration (mg/L)

Solution pH

Percentage
Adsorption
(%)

Mean
Percentage
Adsorption
(%)

2-hour, Sample A

4.59

6.9

55.6

55.6 

2-hour, Sample B

4.60

6.9

55.5

5-hour, Sample A

4.57

6.8

55.9

56.0 

5-hour, Sample B

4.53

6.8

56.2

24-hour, Sample A

4.11

6.7

60.0

59.7 

24-hour, Sample B

4.16

6.8

59.5

48-hour, Sample A

4.02

6.5

61.0

61.8 

48-hour, Sample B

3.86

6.5

62.6

 

Soil Type 3

Solution

Concentration (mg/L)

Solution pH

Percentage
Adsorption
(%)

Mean
Percentage
Adsorption
(%)

2-hour, Sample A

5.03

6.0

51.4

51.4 

2-hour, Sample B

5.04

6.0

51.3

5-hour, Sample A

5.00

6.0

51.7

52.1 

5-hour, Sample B

4.92

6.0

52.5

24-hour, Sample A

4.56

6.1

55.5

56.0 

24-hour, Sample B

4.47

6.1

56.4

48-hour, Sample A

4.33

6.1

58.0

57.9 

48-hour, Sample B

4.35

6.1

57.8

 

Soil Type 4

Solution

Concentration (mg/L)

Solution pH

Percentage
Adsorption
(%)

Mean
Percentage
Adsorption
(%)

2-hour, Sample A

4.01

4.9

62.3

62.6 

2-hour, Sample B

3.93

4.9

63.0

5-hour, Sample A

3.07

4.9

71.0

70.8 

5-hour, Sample B

3.10

4.9

70.7

24-hour, Sample A

2.78

5.0

73.3

72.9

24-hour, Sample B

2.88

5.0

72.4

48-hour, Sample A

3.46

5.1

 67.1[1]

75.6

48-hour, Sample B

2.57

5.1

75.6

 

Soil Type 5 

Solution

Concentration (mg/L)

Solution pH

Percentage
Adsorption
(%)

Mean
Percentage
Adsorption
(%)

2-hour, Sample A

7.96

5.9

23.1

24.4 

2-hour, Sample B

7.69

5.9

25.7

5-hour, Sample A

7.75

5.9

25.1

26.0 

5-hour, Sample B

7.55

5.9

27.0

24-hour, Sample A

7.32

6.1

28.6

28.9 

24-hour, Sample B

7.28

6.1

29.1

48-hour, Sample A

7.10

6.0

31.2

31.5 

48-hour, Sample B

7.04

6.1

31.8

 

Soil Type 7

Solution

Concentration (mg/L)

Solution pH

Percentage
Adsorption
(%)

Mean
Percentage
Adsorption
(%)

2-hour, Sample A

4.62

3.1

56.6

55.6 

2-hour, Sample B

4.83

3.1

54.6

5-hour, Sample A

4.25

3.1

59.8

59.4 

5-hour, Sample B

4.33

3.1

59.0

24-hour, Sample A

3.18

3.0

69.5

69.8 

24-hour, Sample B

3.12

3.0

70.1

48-hour, Sample A

2.82

3.1

73.2

72.9 

48-hour, Sample B

2.89

3.1

72.6

 

The percentage adsorption data for the five soil types is also presented graphically as adsorption equilibration plots.

The pH of the soil-less controls and blank solutions are shown in the following table:

Solution

pH

Solution

pH

Soil-less Control A

6.9

Soil Type 2, Soil Only Blank A

6.6

Soil-less Control B

6.9

Soil Type 2, Soil Only Blank B

6.6

Soil-less Control C

6.9

Soil Type 3, Soil Only Blank A

6.1

Soil-less Control D

7.0

Soil Type 3, Soil Only Blank B

6.2

Soil-less Control E

7.0

Soil Type 4, Soil Only Blank A

5.1

Soil-less Control F

7.0

Soil Type 4, Soil Only Blank B

5.1

Solvent Only Blank A

7.1

Soil Type 5, Soil Only Blank A

6.5

Solvent Only Blank B

7.1

Soil Type 5, Soil Only Blank B

6.5

Solvent Only Blank C

7.0

Soil Type 7, Soil Only Blank A

3.1

Solvent Only Blank D

7.2

Soil Type 7, Soil Only Blank B

3.1

 Determination of Desorption Equilibration Time

The weights/volumes removed and replenished on establishing desorption step testing are shown in the following table: 

Sample Identity

Aqueous Phase Weight/Volume (g or mL)[1]

Volume Removed

Fresh Volume Added

New Total Volume

Soil Type 2, 4-hour, Sample A

10.8177

10.8180

16.0003

Soil Type 2, 4-hour, Sample B

10.6576

10.6690

16.0114

Soil Type 2, 24-hour, Sample A

10.4797

10.4741

15.9944

Soil Type 2, 24-hour, Sample B

10.4182

10.4293

16.0111

Soil Type 2, 48-hour, Sample A

10.4523

10.4623

16.0100

Soil Type 2, 48-hour, Sample B

10.3764

10.3733

15.9969

Soil Type 2, Blank A

10.5472

10.5523

16.0051

Soil Type 2, Blank B

10.4767

10.4870

16.0103

Soil Type 3, 4-hour, Sample A

8.2997

8.3016

16.0019

Soil Type 3, 4-hour, Sample B

8.5406

8.5591

16.0185

Soil Type 3, 24-hour, Sample A

8.6172

8.6296

16.0124

Soil Type 3, 24-hour, Sample B

8.5460

8.5565

16.0105

Soil Type 3, 48-hour, Sample A

8.7028

8.7150

16.0122

Soil Type 3, 48-hour, Sample B

8.7097

8.7324

16.0227

Soil Type 3, Blank A

8.3629

8.3677

16.0048

Soil Type 3, Blank B

8.5000

8.5072

16.0072

Soil Type 4, 4-hour, Sample A

8.0831

8.0971

16.0140

Soil Type 4, 4-hour, Sample B

7.8493

7.8560

16.0064

Soil Type 4, 24-hour, Sample A

8.0630

8.0754

16.0124

Soil Type 4, 24-hour, Sample B

7.9804

7.9810

16.0006

Soil Type 4, 48-hour, Sample A

7.9946

8.0001

16.0055

Soil Type 4, 48-hour, Sample B

8.0539

8.0646

16.0107

Soil Type 4, Blank A

8.0414

8.0648

16.0234

Soil Type 4, Blank B

8.0443

8.0576

16.0133

Soil Type 5, 4-hour, Sample A

9.0632

9.0124

15.9492

Soil Type 5, 4-hour, Sample B

10.0389

10.0350

15.9961

Soil Type 5, 24-hour, Sample A

9.7340

9.7530

16.0190

Soil Type 5, 24-hour, Sample B

10.2286

10.2242

15.9956

Soil Type 5, 48-hour, Sample A

10.0678

10.0756

16.0078

Soil Type 5, 48-hour, Sample B

9.8690

9.8768

16.0078

Soil Type 5, Blank A

10.3627

10.3622

15.9995

Soil Type 5, Blank B

10.0869

10.1202

16.0333

 [1]During sample handling, the method guideline specified that an aqueous phase density of 1.000 g/cm3can be applied such that weights (in g) and volumes (in mL or cm3) are equivalent and interchangeable.

Sample Identity

Aqueous Phase Weight/Volume (g or mL)[2]

Volume Removed

Fresh Volume Added

New Total Volume

Soil Type 7, 4-hour, Sample A

14.4413

14.4613

16.0200

Soil Type 7, 4-hour, Sample B

12.4547

12.4594

16.0047

Soil Type 7, 24-hour, Sample A

12.0048

12.0222

16.0174

Soil Type 7, 24-hour, Sample B

10.3050

10.3083

16.0033

Soil Type 7, 48-hour, Sample A

13.2322

13.2526

16.0204

Soil Type 7, 48-hour, Sample B

14.0024

14.0370

16.0346

Soil Type 7, Blank A

14.7081

14.7050

15.9969

Soil Type 7, Blank B

13.9554

13.9786

16.0232

[2]During sample handling, the method guideline specified that an aqueous phase density of 1.000 can be applied such that weights (in g) and volumes (in mL or cm3) are equivalent and interchangeable.

The mean peak areas relating to the standard, sample, control and blank solutions on analysis following completion of the desorption equilibration periods are shown inAppendix 4.

 

The soil-less control recoveries on completion of the adsorption equilibration period, calculated with respect to each theoretical dosed concentration, are shown in the following tables:

 

Testing of Soil Type 2, Soil Type 3 and Soil Type 5 

Solution

Theoretical Dosed Concentration (mg/L)

Analyzed Concentration (mg/L)

Mean Analyzed Concentration (mg/L)

Recovery
(%)

Mean Recovery
(%)

Control A

10.2

10.2

10.5

99.8

102.9

Control B

10.4

102

Control C

10.9

107

 

Testing of Soil Type 4 and Soil Type 7 

Solution

Theoretical Dosed Concentration (mg/L)

Analyzed Concentration (mg/L)

Mean Analyzed Concentration (mg/L)

Recovery
(%)

Mean Recovery
(%)

Control D

10.2

9.88

10.1

96.7

98.9

Control E

10.0

97.9

Control F

10.5

102

 

The concentration of test item analyzed in each solution on completion of the adsorption equilibrium period, the solution pH and the percentage of test item adsorbed with respect to the analyzed mean control concentration (10.5 mg/L for soil type 2, soil type 3 and soil type 5, and 10.1 mg/L for soil type 4 and soil type 7, respectively) are shown in the following table:

 

Adsorption Step Analysis 

Solution

Concentration (mg/L)

Solution pH

Percentage Adsorption (%)

Soil Type 2, 4-hour, Sample A

3.84

6.9

63.4

Soil Type 2, 4-hour, Sample B

3.89

6.9

62.8

Soil Type 2, 24-hour, Sample A

3.96

7.0

62.2

Soil Type 2, 24-hour, Sample B

3.86

7.0

63.1

Soil Type 2, 48-hour, Sample A

3.94

7.0

62.4

Soil Type 2, 48-hour, Sample B

3.85

7.1

63.3

Soil Type 3, 4-hour, Sample A

4.30

6.5

58.9

Soil Type 3, 4-hour, Sample B

4.40

6.4

58.0

Soil Type 3, 24-hour, Sample A

4.37

6.5

58.3

Soil Type 3, 24-hour, Sample B

4.44

6.4

57.6

Soil Type 3, 48-hour, Sample A

4.38

6.5

58.2

Soil Type 3, 48-hour, Sample B

4.47

6.4

57.4

Soil Type 4, 4-hour, Sample A

2.55

5.2

74.8

Soil Type 4, 4-hour, Sample B

2.62

5.2

74.1

Soil Type 4, 24-hour, Sample A

2.71

5.2

73.2

Soil Type 4, 24-hour, Sample B

2.70

5.2

73.3

Soil Type 4, 48-hour, Sample A

2.71

5.2

73.3

Soil Type 4, 48-hour, Sample B

2.71

5.2

73.3

Soil Type 5, 4-hour, Sample A

7.40

6.2

29.3

Soil Type 5, 4-hour, Sample B

7.08

6.3

32.4

Soil Type 5, 24-hour, Sample A

7.43

6.2

29.1

Soil Type 5, 24-hour, Sample B

7.33

6.2

30.0

Soil Type 5, 48-hour, Sample A

7.33

6.2

30.0

Soil Type 5, 48-hour, Sample B

7.19

6.2

31.4

Soil Type 7, 4-hour, Sample A

2.44

3.1

75.9

Soil Type 7, 4-hour, Sample B

2.74

3.1

72.9

  

Adsorption Step Analysis – Continued

Solution

Concentration (mg/L)

Solution pH

Percentage Adsorption (%)

Soil Type 7, 24-hour, Sample A

2.82

3.1

72.1

Soil Type 7, 24-hour, Sample B

3.00

3.2

70.4

Soil Type 7, 48-hour, Sample A

2.40

3.1

76.3

Soil Type 7, 48-hour, Sample B

2.47

3.2

75.6

 

The concentration of test item analyzed in each solution and the solution pH on completion of the required desorption period are shown in the following table:

Desorption Step Analysis 

Solution

Concentration (mg/L)

Solution pH

Soil Type 2, 4-hour, Sample A

2.69

6.8

Soil Type 2, 4-hour, Sample B

2.68

6.8

Soil Type 2, 24-hour, Sample A

2.76

6.6

Soil Type 2, 24-hour, Sample B

2.75

6.6

Soil Type 2, 48-hour, Sample A

2.63

6.8

Soil Type 2, 48-hour, Sample B

2.54

6.8

Soil Type 3, 4-hour, Sample A

3.21

6.2

Soil Type 3, 4-hour, Sample B

3.23

6.2

Soil Type 3, 24-hour, Sample A

3.18

6.1

Soil Type 3, 24-hour, Sample B

3.18

6.1

Soil Type 3, 48-hour, Sample A

3.01

6.3

Soil Type 3, 48-hour, Sample B

3.07

6.4

Soil Type 4, 4-hour, Sample A

2.13

5.1

Soil Type 4, 4-hour, Sample B

2.18

5.1

Soil Type 4, 24-hour, Sample A

1.95

5.1

Soil Type 4, 24-hour, Sample B

1.97

5.1

Soil Type 4, 48-hour, Sample A

1.92

5.3

Soil Type 4, 48-hour, Sample B

1.90

5.3

Soil Type 5, 4-hour, Sample A

4.04

6.1

Soil Type 5, 4-hour, Sample B

3.77

6.1

Soil Type 5, 24-hour, Sample A

3.88

5.9

Soil Type 5, 24-hour, Sample B

3.72

5.9

Desorption Step Analysis – Continued

Solution

Concentration (mg/L)

Solution pH

Soil Type 5, 48-hour, Sample A

3.70

6.1

Soil Type 5, 48-hour, Sample B

3.78

6.2

Soil Type 7, 4-hour, Sample A

1.63

3.2

Soil Type 7, 4-hour, Sample B

2.06

3.2

Soil Type 7, 24-hour, Sample A

2.24

3.1

Soil Type 7, 24-hour, Sample B

2.46

3.1

Soil Type 7, 48-hour, Sample A

2.14

3.2

Soil Type 7, 48-hour, Sample B

2.07

3.2

 

The solution pH for the control solutions, soil only and solvent only blanks are shown in the following table:

Solution

pH at Adsorption Analysis

pH at Desorption Analysis

Soil-less Control A

6.8

-

Soil-less Control B

6.9

-

Soil-less Control C

6.9

-

Soil-less Control D

6.8

-

Soil-less Control E

6.8

-

Soil-less Control F

6.9

-

Soil Type 2, Soil Only Blank A

7.0

6.6

Soil Type 2, Soil Only Blank B

7.0

6.7

Soil Type 3, Soil Only Blank A

6.4

6.3

Soil Type 3, Soil Only Blank B

6.4

6.3

Soil Type 4, Soil Only Blank A

5.2

5.4

Soil Type 4, Soil Only Blank B

5.2

5.4

Soil Type 5, Soil Only Blank A

6.2

6.2

Soil Type 5, Soil Only Blank B

6.2

6.2

Soil Type 7, Soil Only Blank A

3.1

3.2

Soil Type 7, Soil Only Blank B

3.1

3.2

Solvent Only Blank A

6.8

-

Solvent Only Blank B

6.8

-

Solvent Only Blank C

6.8

-

Solvent Only Blank D

6.8

-

 

The calculated mass of test item adsorbed to the soil phase, the total mass of test item present in each desorption aqueous phase, the mass of test item present in solution due to incomplete removal of the aqueous phase, and the mass of test item desorbed are shown inthe following table:

Soil Type[3]

Sample Identity

Mass Adsorbed
 (µg)

Mass in Solution on Desorption Analysis
 (µg)

Mass Present due to Incomplete Adsorption Aqueous Phase Removal
(µg)

Mass
 Desorbed
 (µg)

2

4-Hr (A)

106

43.1

19.9

23.2

4-Hr (B)

105

42.8

20.8

22.0

24-Hr (A)

104

44.2

21.9

22.3

24-Hr (B)

106

44.0

21.6

22.4

48-Hr (A)

105

42.1

21.8

20.2

48-Hr (B)

106

40.7

21.6

19.0

3

4-Hr (A)

98.8

51.4

33.1

18.3

4-Hr (B)

97.3

51.7

32.8

18.9

24-Hr (A)

97.7

50.9

32.3

18.7

24-Hr (B)

96.6

51.0

33.1

17.9

48-Hr (A)

97.6

48.1

32.0

16.2

48-Hr (B)

96.1

49.2

32.6

16.6

4

4-Hr (A)

121

34.0

20.2

13.9

4-Hr (B)

120

34.8

21.4

13.5

24-Hr (A)

119

31.2

21.5

9.73

24-Hr (B)

119

31.4

21.7

9.76

48-Hr (A)

119

30.7

21.7

9.00

48-Hr (B)

119

30.5

21.5

9.00

5

4-Hr (A)

49.2

64.4

51.4

13.1

4-Hr (B)

54.3

60.3

42.2

18.1

24-Hr (A)

48.8

62.1

46.5

15.6

24-Hr (B)

50.3

59.5

42.3

17.2

48-Hr (A)

50.3

59.3

43.5

15.8

48-Hr (B)

52.6

60.5

44.1

16.4

 

Soil Type*

Sample Identity

Mass Adsorbed
 (µg)

Mass in Solution on Desorption Analysis
 (µg)

Mass Present due to Incomplete Adsorption Aqueous Phase Removal
(µg)

Mass
 Desorbed
 (µg)

7

4-Hr (A)

123

26.1

3.80

22.3

4-Hr (B)

118

32.9

9.71

23.2

24-Hr (A)

117

35.8

11.3

24.6

24-Hr (B)

114

39.4

17.1

22.4

48-Hr (A)

124

34.2

6.64

27.6

48-Hr (B)

122

33.2

4.94

28.3

 

The calculated percentage desorption for each sample and the calculated mean percentage desorption for each desorption equilibrium timepoint are shown in the following table:

 

Soil Type[4]

Desorption Period (hours)

Percentage Desorption (%)

Mean Percentage Desorption (%)

Sample A

Sample B

2

4

21.8

20.9

21.4

24

21.4

21.2

21.3

48

19.3

17.9

18.6

3

4

18.5

19.4

19.0

24

19.1

18.5

18.8

48

16.6

17.3

17.0

4

4

11.5

11.2

11.3

24

8.21

8.23

8.22

48

7.59

7.59

7.59

5

4

 26.5[5]

33.3

33.3

24

32.0

34.2

33.1

48

31.3

31.2

31.2

7

4

18.2

19.7

18.9

24

21.0

19.6

20.3

48

22.3

23.1

22.7

 

The percentage desorption data is presented graphically as desorption equilibration plots.

Calculation of Adsorption Coefficients

The data required for the calculation of the distribution coefficient (Kd) and the organic carbon normalized adsorption coefficient (Koc) is shown in the following table: 

Soil Type[1]

Sample Identity[2]

Dry Mass of Soil[3]
(g)

Volume of Aqueous Phase (cm3)

Percentage Adsorption at Equilibrium (%)

2

4-hour A

15.56

16

63.4

4-hour B

15.52

16

62.8

24-hour A

15.47

16

62.2

24-hour B

15.54

16

63.1

48-hour A

15.56

16

62.4

48-hour B

15.55

16

63.3

3

4-hour A

15.58

16

58.9

4-hour B

15.63

16

58.0

24-hour A

15.63

16

58.3

24-hour B

15.62

16

57.6

48-hour A

15.58

16

58.2

48-hour B

15.56

16

57.4

4

4-hour A

15.53

16

74.8

4-hour B

15.47

16

74.1

24-hour A

15.47

16

73.2

24-hour B

15.49

16

73.3

48-hour A

15.49

16

73.3

48-hour B

15.53

16

73.3

5

4-hour A

15.90

16

29.3

4-hour B

15.87

16

32.4

24-hour A

15.94

16

29.1

24-hour B

15.88

16

30.0

48-hour A

15.91

16

30.0

48-hour B

15.94

16

31.4

[2]Sample identity from determination of desorption equilibrium time. A common adsorption equilibration period of 48-hours was actually applied to all samples.

[3]Corrected for moisture content.

 

Soil Type[1]

Sample Identity[2]

Dry Mass of Soil[3]
(g)

Volume of Aqueous Phase (cm3)

Percentage Adsorption at Equilibrium (%)

7

4-hour A

0.5948

16

75.9

4-hour B

0.5802

16

72.9

24-hour A

0.5915

16

72.1

24-hour B

0.5895

16

70.4

48-hour A

0.5830

16

76.3

48-hour B

0.5826

16

75.6

 

The calculated distribution coefficients (Kd) and organic carbon normalized adsorption coefficients (Koc) at 25 ± 2 ºC, including the mean value for each soil type, are shown in the following tables:

 

Soil Type 2 

Sample
Identity†

Kd
(cm3/g)

Mean Kd
(cm3/g)

Koc
(cm3/g)

Mean Koc
(cm3/g)

Log10Koc

 Mean
Log10Koc

4-hour A

1.78

1.74

68.1

66.8

1.83

1.82

4-hour B

1.74

66.8

1.82

24-hour A

1.70

65.1

1.81

24-hour B

1.76

67.5

1.83

48-hour A

1.71

65.5

1.82

48-hour B

1.77

67.9

1.83

 

Soil Type 3 

Sample
Identity†

Kd
(cm3/g)

Mean Kd
(cm3/g)

Koc
(cm3/g)

Mean Koc
(cm3/g)

Log10Koc

 Mean
Log10Koc

4-hour A

1.47

1.42

33.6

32.4

1.53

1.51

4-hour B

1.42

32.3

1.51

24-hour A

1.43

32.6

1.51

24-hour B

1.39

31.8

1.50

48-hour A

1.43

32.7

1.51

48-hour B

1.38

31.6

1.50

Soil Type 4

 

Sample
Identity[1]

Kd
(cm3/g)

Mean Kd
(cm3/g)

Koc
(cm3/g)

Mean Koc
(cm3/g)

Log10Koc

 Mean
Log10Koc

4-hour A

3.06

2.89

 

79.8

75.2

 

1.90

1.88

4-hour B

2.96

77.0

1.89

24-hour A

2.83

73.7

1.87

24-hour B

2.83

73.8

1.87

48-hour A

2.83

73.7

1.87

48-hour B

2.82

73.5

1.87

 

Table28– Soil Type 5

 

Sample
Identity*

Kd
(cm3/g)

Mean Kd
(cm3/g)

Koc
(cm3/g)

Mean Koc
(cm3/g)

Log10Koc

 Mean
Log10Koc

4-hour A

0.418

0.439

37.3

39.2

1.57

1.59

4-hour B

0.483

43.1

1.63

24-hour A

0.412

36.8

1.57

24-hour B

0.432

38.6

1.59

48-hour A

0.431

38.5

1.59

48-hour B

0.459

41.0

1.61

 

Soil Type 7

Sample
Identity*

Kd
(cm3/g)

Mean Kd
(cm3/g)

Koc
(cm3/g)

Mean Koc
(cm3/g)

Log10Koc

 Mean
Log10Koc

4-hour A

84.6

77.8

338

310

2.53

2.49

4-hour B

74.3

297

2.47

24-hour A

69.9

279

2.45

24-hour B

64.4

257

2.41

48-hour A

88.4

353

2.55

48-hour B

84.9

339

2.53

The distribution coefficient (Kd) and the organic carbon normalized adsorption coefficient (Koc) results are summarized in the following table:

Soil Type[1]

Mean Distribution
 Coefficient for Adsorption
(Kd,cm3/g)

Mean Organic Carbon Normalized Adsorption Coefficient
(Koc, cm3/g)

Log10Koc

2

1.74

66.8

1.82

3

1.42

32.4

1.51

4

2.89

75.2

1.88

5

0.439

39.2

1.59

7

77.8

310

2.49

 

Soil Type*

Mean Distribution
 Coefficient for Adsorption
(Kd,cm3/g)

Mean Organic Carbon Normalized Adsorption Coefficient
(Koc, cm3/g)

Log10Koc

2

1.74

66.8

1.82

3

1.42

32.4

1.51

4

2.89

75.2

1.88

5

0.439

39.2

1.59

7

77.8

310

2.49

Overall Kdrange:      0.439 to 77.8 cm3/g

Overall Kocrange:     32.4 to 310 cm3/g
log10Kocrange:         1.51 to 2.49

Calculation of Desorption Coefficients

The data required for the calculation of the apparent desorption coefficient (Kdes) and the organic carbon normalized apparent desorption coefficient (Kdes (oc)) is shown in the following table

Soil Type[1]

Sample Identity

Mass of Test Item Adsorbed (µg)

Mass of Test Item Desorbed (µg)

Dry Mass of
Soil[2](g)

Volume of Aqueous Phase (cm3)

2

4-hour A

106

23.2

15.56

16.0003

4-hour B

105

22.0

15.52

16.0114

24-hour A

104

22.3

15.47

15.9944

24-hour B

106

22.4

15.54

16.0111

48-hour A

105

20.2

15.56

16.0100

48-hour B

106

19.0

15.55

15.9969

3

4-hour A

98.8

18.3

15.58

16.0019

4-hour B

97.3

18.9

15.63

16.0185

24-hour A

97.7

18.7

15.63

16.0124

24-hour B

96.6

17.9

15.62

16.0105

48-hour A

97.6

16.2

15.58

16.0122

48-hour B

96.1

16.6

15.56

16.0227

4

4-hour A

121

13.9

15.53

16.0140

4-hour B

120

13.5

15.47

16.0067

24-hour A

119

9.73

15.47

16.0124

24-hour B

119

9.76

15.49

16.0006

48-hour A

119

9.00

15.49

16.0055

48-hour B

119

9.00

15.53

16.0107

5

4-hour A[3]

49.2

13.1

15.90

15.9492

4-hour B

54.3

18.1

15.87

15.9961

24-hour A

48.8

15.6

15.94

16.0190

24-hour B

50.3

17.2

15.88

15.9956

48-hour A

50.3

15.8

15.91

16.0078

48-hour B

52.6

16.4

15.94

16.0078

Soil Type[1]

Sample Identity

Mass of Test Item Adsorbed (µg)

Mass of Test Item Desorbed (µg)

Dry Mass of
Soil[2](g)

Volume of Aqueous Phase (cm3)

7

4-hour A

123

22.3

0.5948

16.0200

4-hour B

118

23.2

0.5802

16.0047

24-hour A

117

24.6

0.5915

16.0174

24-hour B

114

22.4

0.5895

16.0033

48-hour A

124

27.6

0.5830

16.0204

48-hour B

122

28.3

0.5826

16.0346

 

The calculated apparent desorption coefficient (Kdes) and organic carbon normalized apparent desorption coefficient (Kdes (oc)) at 25 ± 2 ºC, including the mean value for each soil type, are shown in the following tables:

 

Soil Type 2 

Sample Identity

Kdes
(cm3/g)

Mean Kdes
(cm3/g)

Kdes (oc) (cm3/g)

Mean
Kdes (oc) (cm3/g)

Log10
Kdes (oc) 

Mean Log10Kdes (oc) 

4-hour A

3.69

4.04

141

155

2.15

2.19

4-hour B

3.90

149

2.17

24-hour A

3.80

146

2.16

24-hour B

3.84

147

2.17

48-hour A

4.30

165

2.22

48-hour B

4.71

180

2.26

 

Soil Type 3 

Sample Identity

Kdes
(cm3/g)

Mean Kdes
(cm3/g)

Kdes (oc) (cm3/g)

Mean
Kdes (oc) (cm3/g)

Log10
Kdes (oc) 

Mean Log10Kdes (oc) 

4-hour A

4.53

4.62

103

105

2.01

2.02

4-hour B

4.25

96.9

1.99

24-hour A

4.34

99.0

2.00

24-hour B

4.52

103

2.01

48-hour A

5.17

118

2.07

48-hour B

4.92

112

2.05

Soil Type 4 

Sample Identity

Kdes
(cm3/g)

Mean Kdes
(cm3/g)

Kdes (oc) (cm3/g)

Mean
Kdes (oc) (cm3/g)

Log10
Kdes (oc) 

Mean Log10Kdes (oc) 

4-hour A

7.97

10.7

208

279

2.32

2.44

4-hour B

8.18

213

2.33

24-hour A

11.6

302

2.48

24-hour B

11.5

300

2.48

48-hour A

12.6

328

2.52

48-hour B

12.6

327

2.51

 

Soil Type 5 

Sample Identity

Kdes
(cm3/g)

Mean Kdes
(cm3/g)

Kdes (oc) (cm3/g)

Mean
Kdes (oc) (cm3/g)

Log10
Kdes (oc) 

Mean Log10Kdes (oc) 

4-hour B

2.02

2.10

180

188

2.26

2.27

24-hour A

2.14

191

2.28

24-hour B

1.94

173

2.24

48-hour A

2.21

197

2.29

48-hour B

2.22

198

2.30

 

Soil Type 7 

Sample Identity

Kdes
(cm3/g)

Mean Kdes
(cm3/g)

Kdes (oc) (cm3/g)

Mean
Kdes (oc) (cm3/g)

Log10
Kdes (oc) 

Mean Log10Kdes (oc) 

4-hour A

121

106

485

422

2.69

2.62

4-hour B

113

450

2.65

24-hour A

102

406

2.61

24-hour B

111

444

2.65

48-hour A

95.6

382

2.58

48-hour B

91.4

365

2.56

 

The apparent desorption coefficient (Kdes) and the organic carbon normalized apparent desorption coefficient (Kdes (oc)) results are summarized in the following table: 

Soil Type[1]

Mean Apparent Desorption Coefficient
(Kdesin cm3/g)

Mean Organic Carbon Normalized Desorption Coefficient
(Kdes (oc)incm3/g)

Log10Organic Carbon Normalized Desorption Coefficient
(Kdes (oc))

2

4.04

155

2.19

3

4.62

105

2.02

4

10.7

279

2.44

5

2.10

188

2.27

7

106

422

2.62

 

The observed percentage desorption data is summarized in the following table:

Soil Type*

Sample Identity /Desorption Period (hours)

Percentage Desorption (%)

Timepoint Mean Percentage Desorption (%)

Overall Mean Percentage Desorption (%)

2

4-Hr Replicate A

21.8

21.4 

20.4

4-Hr Replicate B

20.9

24-Hr Replicate A

21.4

21.3 

24-Hr Replicate B

21.2

48-Hr Replicate A

19.3

18.6

48-Hr Replicate B

17.9

3

4-Hr Replicate A

18.5

19.0 

18.2

4-Hr Replicate B

19.4

24-Hr Replicate A

19.1

18.8 

24-Hr Replicate B

18.5

48-Hr Replicate A

16.6

17.0

48-Hr Replicate B

17.3

4

4-Hr Replicate A

11.5

11.3 

9.05

4-Hr Replicate B

11.2

24-Hr Replicate A

8.21

8.22 

24-Hr Replicate B

8.23

48-Hr Replicate A

7.59

7.59

48-Hr Replicate B

7.59

Soil Type[1]

Sample Identity /Desorption Period (hours)

Percentage Desorption (%)

Timepoint Mean Percentage Desorption (%)

Overall Mean Percentage Desorption (%)

5

 4-Hr Replicate A[2]

not applicable

33.3

32.4

4-Hr Replicate B

33.3

24-Hr Replicate A

32.0

33.1 

24-Hr Replicate B

34.2

48-Hr Replicate A

31.3

31.2

48-Hr Replicate B

31.2

7

4-Hr Replicate A

18.2

18.9

20.7

 

4-Hr Replicate B

19.7

24-Hr Replicate A

21.0

20.3

24-Hr Replicate B

19.6

48-Hr Replicate A

22.3

22.7

48-Hr Replicate B

23.1

Soil Type*

Observed Mean Percentage Desorption (%)

Mean Apparent Desorption Coefficient
(Kdesin cm3/g)

Mean Organic Carbon Normalized Desorption Coefficient
(Kdes (oc)incm3/g)

Log10Organic Carbon Normalized Desorption Coefficient
(Kdes (oc))

2

20.4

4.04

155

2.19

3

18.2

4.62

105

2.02

4

9.05

10.7

279

2.44

 

Soil Type*

Observed Mean Percentage Desorption (%)

Mean Apparent Desorption Coefficient
(Kdesin cm3/g)

Mean Organic Carbon Normalized Desorption Coefficient
(Kdes (oc)incm3/g)

Log10Organic Carbon Normalized Desorption Coefficient
(Kdes (oc))

5

32.4

2.10

188

2.27

7

20.7

106

422

2.62

Determination of Adsorption Isotherms

The concentration (mg/L) of test item analyzed in each soil-less control solution and the percentage recovery with respect to the theoretical fortified concentration are shown in the following tables:

 

Solution

Theoretical Dosed Concentration (mg/L)

Concentration
 (mg/L)

Mean Analyzed Concentration (mg/L)

Percentage of Theoretical (%)[1]

1.0 mg/L, Soil-less Control A

1.06

0.989

1.010

93.6

1.0 mg/L, Soil-less Control B

1.00

95.1

1.0 mg/L, Soil-less Control C

1.04

98.3

3.0 mg/L, Soil-less Control A

3.17

3.04

3.05

96.0

3.0 mg/L, Soil-less Control B

3.06

96.7

3.0 mg/L, Soil-less Control C

3.04

95.8

30 mg/L, Soil-less Control A

30.1

33.9

34.0

113

30 mg/L, Soil-less Control B

34.4

114

30 mg/L, Soil-less Control C

33.8

112

100 mg/L, Soil-less Control A

100

119

116

118

100 mg/L, Soil-less Control B

117

117

100 mg/L, Soil-less Control C

111

111

 

The concentration (mg/L) of test item analyzed in each sample, the solution pH and the percentage of test item adsorbed with respect to the relevant mean soil-less control concentration are shown in the following tables:

 

1.0 mg/L Fortification Concentration Adsorption Data

Solution

Concentration (mg/L)

Solution pH

Percentage
Adsorption
(%)

Mean
Percentage
Adsorption
(%)

Soil Type 2, Sample A

0.226

7.5

77.6

77.8

Soil Type 2, Sample B

0.222

7.5

78.0

Soil Type 3, Sample A

0.372

6.5

63.2

63.0

Soil Type 3, Sample B

0.375

6.5

62.9

Soil Type 4, Sample A

0.225

5.6

77.7

78.0

Soil Type 4, Sample B

0.220

5.4

78.2

Soil Type 5, Sample A

0.636

6.4

37.0

37.2

Soil Type 5, Sample B

0.633

6.6

37.3

Soil Type 7, Sample A

0.213

3.1

79.0

78.4

Soil Type 7, Sample B

0.223

3.1

77.9

 

3.0 mg/L Fortification Concentration Adsorption Data

Solution

Concentration (mg/L)

Solution pH

Percentage
Adsorption
(%)

Mean
Percentage
Adsorption
(%)

Soil Type 2, Sample A

0.775

7.5

74.6

74.8

Soil Type 2, Sample B

0.759

7.5

75.1

Soil Type 3, Sample A

1.23

6.5

59.8

59.9

Soil Type 3, Sample B

1.22

6.5

60.0

Soil Type 4, Sample A

0.726

5.5

76.2

74.9

Soil Type 4, Sample B

0.803

5.5

73.6

Soil Type 5, Sample A

2.01

6.4

34.1

32.9

Soil Type 5, Sample B

2.08

6.5

31.7

Soil Type 7, Sample A

0.707

3.1

76.8

76.7

Soil Type 7, Sample B

0.713

3.1

76.6

 

30 mg/L Fortification Concentration Adsorption Data

Solution

Concentration (mg/L)

Solution pH

Percentage
Adsorption
(%)

Mean
Percentage
Adsorption
(%)

Soil Type 2, Sample A

11.4

7.6

66.5

66.1

Soil Type 2, Sample B

11.7

7.6

65.6

Soil Type 3, Sample A

15.0

6.8

56.0

55.2

Soil Type 3, Sample B

15.5

6.8

54.5

Soil Type 4, Sample A

8.75

5.6

74.3

73.7

Soil Type 4, Sample B

9.12

6.0

73.2

Soil Type 5, Sample A

24.1

6.6

29.3

28.4

Soil Type 5, Sample B

24.7

6.6

27.5

Soil Type 7, Sample A[2]

19.1

3.2

44.0

67.0

Soil Type 7, Sample B

11.2

3.2

67.0

 

100 mg/L Fortification Concentration Adsorption Data

Solution

Concentration (mg/L)

Solution pH

Percentage
Adsorption
(%)

Mean
Percentage
Adsorption
(%)

Soil Type 2, Sample A

42.8

7.6

63.0

62.8

Soil Type 2, Sample B

43.1

7.6

62.7

Soil Type 3, Sample A

53.5

6.8

53.7

52.6

Soil Type 3, Sample B

56.0

6.8

51.5

Soil Type 4, Sample A

31.6

5.9

72.7

72.6

Soil Type 4, Sample B

31.8

5.8

72.5

Soil Type 5, Sample A

82.5

6.6

28.6

28.2

Soil Type 5, Sample B

83.3

6.6

27.9

Soil Type 7, Sample A

39.8

3.2

65.5

65.0

Soil Type 7, Sample B

40.9

3.2

64.6

The pH of the soil and solvent only blanks are shown in the following table:

  

Blank

Solution pH

A

B

C

D

Soil Type 2, Soil Only Blank

7.4

7.4

7.5

7.5

Soil Type 3, Soil Only Blank

6.7

6.7

6.8

6.8

Soil Type 4, Soil Only Blank

5.5

5.5

5.6

5.6

Soil Type 5, Soil Only Blank

6.8

6.8

6.7

6.7

Soil Type 7, Soil Only Blank

3.1

3.1

3.2

3.2

Solvent Only Blank

6.7

6.7

6.8

6.8

 

The pH of the soil-less control solutions are shown in the following table:

 

Solution

Solution pH

Solution

Solution pH

1.0 mg/L, Soil-less Control A

6.7

30 mg/L, Soil-less Control A

6.8

1.0 mg/L, Soil-less Control B

6.7

30 mg/L, Soil-less Control B

6.8

1.0 mg/L, Soil-less Control C

6.7

30 mg/L, Soil-less Control C

6.8

3.0 mg/L, Soil-less Control A

6.9

100 mg/L, Soil-less Control A

6.9

3.0 mg/L, Soil-less Control B

6.9

100 mg/L, Soil-less Control B

6.9

3.0 mg/L, Soil-less Control C

6.9

100 mg/L, Soil-less Control C

6.9

 

The calculated dry mass of soil in each sample, the total mass of test item adsorbed and the mass adsorbed per unit mass of soil, are shown in the following table:

 

Soil Type

Nominal Concentration
(mg/L)

Dry Mass of
Soil[3](g)

Total Mass Adsorbed
(µg)

Mass Adsorbed Per Unit Mass of Soil (µg/g)

2

1.0

(A)

15.47

12.5

0.810

1.0

(B)

15.54

12.6

0.811

3.0

(A)

15.57

36.4

2.34

3.0

(B)

15.47

36.6

2.37

10

(A)

15.47

104

6.74

10

(B)

15.54

106

6.81

 

Soil Type

Nominal Concentration
(mg/L)

Dry Mass of
Soil[4](g)

Total Mass Adsorbed
(µg)

Mass Adsorbed Per Unit Mass of Soil (µg/g)

2

30

(A)

14.52

339

23.4

30

(B)

14.55

335

23.0

100

(A)

14.54

1.09 x 103

75.0

100

(B)

14.51

1.09 x 103

74.9

3

1.0

(A)

15.56

10.2

0.656

1.0

(B)

15.57

10.2

0.653

3.0

(A)

15.58

29.1

1.87

3.0

(B)

15.58

29.3

1.88

10

(A)

15.63

97.7

6.25

10

(B)

15.62

96.6

6.18

30

(A)

14.58

286

19.6

30

(B)

14.63

278

19.0

100

(A)

14.59

930

63.8

100

(B)

14.66

893

60.9

4

1.0

(A)

15.51

12.6

0.810

1.0

(B)

15.46

12.6

0.818

3.0

(A)

15.49

37.1

2.40

3.0

(B)

15.48

35.9

2.32

10

(A)

15.47

119

7.66

10

(B)

15.49

119

7.66

30

(A)

14.50

379

26.1

30

(B)

14.55

374

25.7

100

(A)

14.50

1.26 x 103

86.8

100

(B)

14.49

1.26 x 103

86.7

5

1.0

(A)

15.95

5.98

0.375

1.0

(B)

15.92

6.03

0.379

3.0

(A)

15.93

16.6

1.04

3.0

(B)

15.91

15.4

0.970

10

(A)

15.94

48.8

3.06

10

(B)

15.88

50.3

3.17

30

(A)

14.94

149

9.99

30

(B)

14.94

140

9.39

 

Soil Type

Nominal Concentration
(mg/L)

Dry Mass of
Soil[5](g)

Total Mass Adsorbed
(µg)

Mass Adsorbed Per Unit Mass of Soil (µg/g)

5

100

(A)

14.95

495

33.1

100

(B)

14.94

484

32.4

7

1.0

(A)

0.5946

12.8

21.5

1.0

(B)

0.5909

12.6

21.3

3.0

(A)

0.5846

37.4

64.0

3.0

(B)

0.5897

37.3

63.3

10

(A)

0.5915

117

197

10

(B)

0.5895

114

193

30

 (A)[6]

not applicable

not applicable

not applicable

30

(B)

0.5552

342

616

100

(A)

0.5526

1.14 x 103

2.06 x 103

100

(B)

0.5485

1.12 x 103

2.04 x 103

 

The mean mass of test item adsorbed per unit mass of soil and the mean concentration remaining in aqueous solution on completion of the adsorption equilibration period are shown in the following table:

  

Soil Type

Nominal Concentration
(mg/L)

Mean Mass of Test Item Adsorbed Per Unit Mass of Soil (µg/g)

Mean Concentration Remaining in Aqueous Solution
(µg/cm3)

2

1.0

0.811

0.224

3.0

2.35

0.767

10

6.77

3.91

30

23.2

11.6

100

74.9

43.0

3

1.0

0.654

0.373

3.0

1.87

1.22

10

6.22

4.41

30

19.3

15.2

100

62.3

54.7

 

Soil Type

Nominal Concentration
(mg/L)

Mean Mass of Test Item Adsorbed Per Unit Mass of Soil (µg/g)

Mean Concentration Remaining in Aqueous Solution
(µg/cm3)

4

1.0

0.814

0.223

3.0

2.36

0.765

10

7.66

2.71

30

25.9

8.94

100

86.7

31.7

5

1.0

0.377

0.635

3.0

1.01

2.05

10

3.12

7.38

30

9.69

24.4

100

32.7

82.9

7

1.0

21.4

0.218

3.0

63.7

0.710

10

195

2.91

30

616

11.2

100

2.05 x 103

40.4

 

The data shown in the previous table has been plotted graphically as normal Freundlich adsorption plots. The data has also been processed using logarithmic transformation and the results are shown in the following table:

 

Soil Type

Nominal Concentration
(mg/L)

Log10[Mean Mass of Test Item Adsorbed Per Unit Mass of Soil (µg/g)]

Log10[Mean Concentration Remaining in Aqueous Solution (µg/cm3)]

2

1.0

-9.11 x 10-2

-0.649

3.0

0.371

-0.115

10

0.831

0.593

30

1.37

1.06

100

1.88

1.63

3

1.0

-0.184

-0.428

3.0

0.273

8.73 x 10-2

10

0.794

0.644

30

1.29

1.18

100

1.80

1.74

Soil Type

Nominal Concentration
(mg/L)

Log10[Mean Mass of Test Item Adsorbed Per Unit Mass of Soil (µg/g)]

Log10[Mean Concentration Remaining in Aqueous Solution (µg/cm3)]

4

1.0

-8.95 x 10-2

-0.653

3.0

0.373

-0.117

10

0.884

0.432

30

1.41

0.951

100

1.94

1.50

5

1.0

-0.424

-0.198

3.0

2.74 x 10-3

0.311

10

0.494

0.868

30

0.986

1.39

100

1.52

1.92

7

1.0

1.33

-0.662

3.0

1.80

-0.149

10

2.29

0.464

30

2.79

1.05

100

3.31

1.61

 

The data shown in the previous table has been plotted graphically as linearized Freundlich adsorption plots.


From the linearized Freundlich adsorption plots, seeFigure 16toFigure 20inclusive, the Freundlich adsorption coefficient was determined for each soil type. The results and the coefficient of determination (r2) of each plot are shown inthe following table:

 

Soil Type*

Intercept

Freundlich Adsorption Coefficient K 
(µg1-1/n(cm3)1/ng-1)

Freundlich Exponent

r2

Organic Carbon Normalized Adsorption Coefficient, K
(µg1-1/n(cm3)1/ng-1)

2

0.439

2.75

0.854

0.993

105

3

0.202

1.59

0.916

1.000

36.3

4

0.503

3.18

0.948

0.999

82.9

5

-0.270

0.537

0.916

0.999

47.9

7

1.91

80.6

0.862

0.999

322

Determination of Desorption Isotherms

The concentration of test item analyzed in each solution, solution pH and percentage desorption at desorption equilibrium are shown in the following tables:

 

1.0 mg/L Fortification Concentration Desorption Data

Solution

Concentration (mg/L)

Solution pH

Percentage
Desorption (%)

Mean
Percentage
Desorption (%)

Soil Type 2, Sample A

0.174

6.8

8.49

8.77

Soil Type 2, Sample B

0.177

6.9

9.05

Soil Type 3, Sample A

0.260

6.2

14.3

14.1

Soil Type 3, Sample B

0.265

6.1

13.8

Soil Type 4, Sample A

0.164

5.3

6.81

6.89

Soil Type 4, Sample B

0.165

5.3

7.00

Soil Type 5, Sample A

0.339

6.1

29.0

28.8

Soil Type 5, Sample B

0.347

6.1

28.5

Soil Type 7, Sample A

0.162

3.2

13.3

14.4

Soil Type 7, Sample B

0.169

3.2

15.4

 

Table56– 3.0 mg/L Fortification Concentration Desorption Data

 

Solution

Concentration (mg/L)

Solution pH

Percentage
Desorption (%)

Mean
Percentage
Desorption (%)

Soil Type 2, Sample A

0.610

6.8

10.6

10.4

Soil Type 2, Sample B

0.591

6.9

10.2

Soil Type 3, Sample A

0.886

6.1

16.9

17.8

Soil Type 3, Sample B

0.910

6.2

18.8

Soil Type 4, Sample A

0.513

5.3

6.93

6.39

Soil Type 4, Sample B

0.530

5.3

5.85

Soil Type 5, Sample A

1.07

6.0

34.3

34.5

Soil Type 5, Sample B

1.12

6.1

34.6

Soil Type 7, Sample A

0.540

3.2

14.0

13.3

Soil Type 7, Sample B

0.522

3.2

12.5

30 mg/L Fortification Concentration Desorption Data

Solution

Concentration (mg/L)

Solution pH

Percentage
Desorption (%)

Mean
Percentage
Desorption (%)

Soil Type 2, Sample A

8.52

6.8

13.0

13.1

Soil Type 2, Sample B

8.74

6.8

13.1

Soil Type 3, Sample A

10.9

6.2

20.4

20.3

Soil Type 3, Sample B

11.0

6.2

20.2

Soil Type 4, Sample A

7.11

5.4

11.1

11.1

Soil Type 4, Sample B

7.22

5.4

11.1

Soil Type 5, Sample A

12.5

6.1

39.7

39.7

Soil Type 5, Sample B

12.7

6.1

39.7

Soil Type 7, Sample A[1]

not applicable

3.2

not applicable

20.1

Soil Type 7, Sample B

7.56

3.2

20.1

 

100 mg/L Fortification Concentration Desorption Data

Solution

Concentration (mg/L)

Solution pH

Percentage
Desorption (%)

Mean
Percentage
Desorption (%)

Soil Type 2, Sample A

31.3

6.8

15.6

15.0

Soil Type 2, Sample B

31.2

6.8

14.4

Soil Type 3, Sample A

37.4

6.2

20.7

20.1

Soil Type 3, Sample B

39.0

6.2

19.4

Soil Type 4, Sample A

26.0

5.4

12.2

12.1

Soil Type 4, Sample B

25.8

5.4

12.0

Soil Type 5, Sample A

41.9

6.1

35.0

35.2

Soil Type 5, Sample B

42.1

6.1

35.4

Soil Type 7, Sample A

24.6

3.2

20.5

21.7

Soil Type 7, Sample B

25.9

3.2

22.8

 

The pH of the soil only blanks are shown in the following table:

 

Blank

Solution pH

A

B

C

D

Soil Type 2, Soil Only Blank

6.9

6.9

6.8

6.8

Soil Type 3, Soil Only Blank

6.2

6.2

6.2

6.2

Soil Type 4, Soil Only Blank

5.2

5.3

5.3

5.3

Soil Type 5, Soil Only Blank

6.0

6.1

6.1

6.1

Soil Type 7, Soil Only Blank

3.2

3.2

3.2

3.2

 

The total mass of test item in solution at desorption equilibrium, the mass of test item present due to incomplete removal of the aqueous phase at adsorption equilibrium, the mass of test item desorbed and the mass desorbed per unit mass of soil are shown in the following table.

 

Soil Type

Nominal Conc.
(mg/L)

Dry Mass of
Soil[2](g)

Mass in Solution After Desorption (µg)

Mass in Solution From Adsorption Aqueous Phase (µg)

Mass Desorbed (µg)

Mass Desorbed per Unit Mass of Soil (µg/g)

2

1.0

(A)

15.47

2.79

1.73

1.06

6.88 x 10-2

1.0

(B)

15.54

2.83

1.69

1.14

7.34 x 10-2

3.0

(A)

15.57

9.76

5.89

3.87

0.249

3.0

(B)

15.47

9.45

5.70

3.75

0.242

10

(A)

15.47

44.2

21.9

22.3

1.44

10

(B)

15.54

44.0

21.6

22.4

1.44

30

(A)

14.52

128

83.7

44.1

3.03

30

(B)

14.55

131

87.2

44.0

3.02

100

(A)

14.54

474

304

170

11.7

100

(B)

14.51

468

312

156

10.8

3

1.0

(A)

15.56

4.17

2.71

1.46

9.39 x 10-2

1.0

(B)

15.57

4.25

2.85

1.41

9.02 x 10-2

3.0

(A)

15.58

14.2

9.23

4.92

0.316

3.0

(B)

15.58

14.6

9.12

5.49

0.352

10

(A)

15.63

50.9

32.3

18.7

1.19

10

(B)

15.62

51.0

33.1

17.9

1.14

 

Soil Type

Nominal Conc.
(mg/L)

Dry Mass of
Soil[3](g)

Mass in Solution After Desorption (µg)

Mass in Solution From Adsorption Aqueous Phase (µg)

Mass Desorbed (µg)

Mass Desorbed per Unit Mass of Soil (µg/g)

3

30

(A)

14.58

164

106

58.1

3.99

30

(B)

14.63

165

109

56.2

3.84

100

(A)

14.59

561

369

192

13.2

100

(B)

14.66

585

412

174

11.8

4

1.0

(A)

15.51

2.62

1.77

0.854

5.51 x 10-2

1.0

(B)

15.46

2.65

1.76

0.882

5.71 x 10-2

3.0

(A)

15.49

8.20

5.63

2.57

0.166

3.0

(B)

15.48

8.49

6.39

2.10

0.136

10

(A)

15.47

31.2

21.5

9.73

0.629

10

(B)

15.49

31.4

21.7

9.76

0.630

30

(A)

14.50

107

64.4

42.2

2.91

30

(B)

14.55

109

67.2

41.3

2.84

100

(A)

14.50

392

238

154

10.6

100

(B)

14.49

388

238

150

10.4

5

1.0

(A)

15.95

5.44

3.70

1.73

0.109

1.0

(B)

15.92

5.54

3.82

1.72

0.108

3.0

(A)

15.93

17.2

11.5

5.71

0.358

3.0

(B)

15.91

18.0

12.7

5.34

0.336

10

(A)

15.94

62.1

46.5

15.6

0.979

10

(B)

15.88

59.5

42.3

17.2

1.08

30

(A)

14.94

187

128

59.2

3.96

30

(B)

14.94

191

135

55.7

3.73

100

(A)

14.95

630

456

173

11.6

100

(B)

14.94

632

461

171

11.5

7

1.0

(A)

0.5946

2.59

0.897

1.70

2.85

1.0

(B)

0.5909

2.70

0.763

1.94

3.28

3.0

(A)

0.5846

8.64

3.39

5.25

8.98

3.0

(B)

0.5897

8.40

3.72

4.68

7.94

10

(A)

0.5915

35.8

11.3

24.6

41.5

10

(B)

0.5895

39.4

17.1

22.4

37.9

  

Soil Type

Nominal Conc.
(mg/L)

Dry Mass of
Soil[4](g)

Mass in Solution After Desorption (µg)

Mass in Solution From Adsorption Aqueous Phase (µg)

Mass Desorbed (µg)

Mass Desorbed per Unit Mass of Soil (µg/g)

7

30

 (A)[5]

not applicable

not applicable

not applicable

not applicable

not applicable

30

(B)

0.5552

113.4

44.8

68.7

124

100

(A)

0.5526

370

138

232

420

100

(B)

0.5485

390

134

255

466

The mean mass of test item desorbed per unit mass of soil and the mean concentration in aqueous solution at desorption equilibrium are shown in the following table:

 

 

Soil Type

Nominal Concentration
(mg/L)

Mean Mass of Test Item Desorbed Per Unit Mass of Soil (µg/g)

Mean Total Remaining Concentration in
Aqueous Solution 
(µg/cm3)

 

2

1.0

7.11 x 10-2

0.176

 

3.0

0.245

0.601

 

10

1.44

2.75

 

30

3.03

8.63

 

100

11.2

31.3

3

1.0

9.20 x 10-2

0.263

3.0

0.334

0.898

10

1.17

3.18

30

3.91

11.0

100

12.5

38.2

4

1.0

5.61 x 10-2

0.165

3.0

0.151

0.521

10

0.630

1.96

30

2.88

7.16

100

10.5

25.9

       

Soil Type

Nominal Concentration
(mg/L)

Mean Mass of Test Item Desorbed Per Unit Mass of Soil (µg/g)

Mean Total Remaining Concentration in
Aqueous Solution 
(µg/cm3)

5

1.0

0.108

0.343

3.0

0.347

1.10

10

1.03

3.80

30

3.85

12.6

100

11.5

42.0

7

1.0

3.07

0.166

3.0

8.46

0.531

10

39.7

2.35

30

124

7.56

100

443

25.3

 

The data shown in the previous table has been plotted graphically as normal Freundlich desorption plot. The data has also been processed using logarithmic transformation and the results are shown in the following table:

 

Soil Type

Nominal Concentration
(mg/L)

Log10 [Mean Mass of Test Item Desorbed Per Unit Mass of Soil (µg/g)]

Log10 [Mean Concentration in Aqueous Solution (µg/cm3)]

2

1.0

-1.15

-0.755

3.0

-0.610

-0.222

10

0.158

0.440

30

0.481

0.936

100

1.05

1.50

3

1.0

-1.04

-0.581

3.0

-0.476

-4.67 x 10-2

10

6.76 x 10-2

0.503

30

0.592

1.04

100

1.10

1.58

4

1.0

-1.25

-0.784

3.0

-0.821

-0.283

10

-0.201

0.292

30

0.459

0.855

100

1.02

1.41

 

Soil Type

Nominal Concentration
(mg/L)

Log10 [Mean Mass of Test Item Desorbed Per Unit Mass of Soil (µg/g)]

Log10 [Mean Concentration in Aqueous Solution (µg/cm3)]

5

1.0

-0.965

-0.465

3.0

-0.460

4.09 x 10-2

10

1.32 x 10-2

0.580

30

0.585

1.10

100

1.06

1.62

7

1.0

0.487

-0.781

3.0

0.927

-0.275

10

1.60

0.371

30

2.09

0.879

100

2.65

1.40

The data shown in the previous table has been plotted graphically as linearized Freundlich desorption plots.

From the linearized Freundlich desorption plot, the Freundlich desorption coefficient was determined for each soil type. The results and the coefficient of determination (r2) of each plot are shown in the following table:



Soil Type*

Intercept

Freundlich Desorption Coefficient K
(µg1-1/n(cm3)1/ng-1)

Freundlich Exponent

r2

Organic Carbon Normalized Desorption Coefficient, K
(µg1-1/n(cm3)1/ng-1)

2

-0.382

0.415

0.973

0.995

15.9

3

-0.443

0.360

0.986

1.000

8.23

4

-0.474

0.336

1.05

0.998

8.75

5

-0.514

0.307

0.974

0.999

27.4

7

1.23

17.1

0.993

0.999

68.3


Validity criteria fulfilled:
yes
Conclusions:
Identification of Optimal Soil to Solution Ratio
The percentage of test item adsorbed after equilibration at 25 ± 2 ºC for 24-hours was investigated using a number of soil to solution ratios. The results are summarized in the following table:

Summary of Influence of Soil to Solution Ratio of Percentage Adsorption
Nominal Soil to Solution Ratio Mean Percentage Test Item Adsorbed (%)
Soil Type 2 Soil Type 5 Soil Type 7
1:2 42.9 13.1 not applicable
1:10 13.7 < 2.0 86.4
1:25 4.67 < 2.0 69.3
1:100 not applicable not applicable 32.8

The experimental results indicated that a soil to solution ratio of 1:1, 1:1 and 1:25 would optimize future analytical results for soil type 2, soil type 5, and soil type 7 respectively. For the remaining two soil types (soil type 3 and soil type 4) a soil to solution ratio of 1:1 was selected for testing based on the organic carbon content of the soils.

Determination of Adsorption Equilibration Time
The evaluation of adsorption equilibrium time indicated that an adsorption period of 48-hours was sufficient to achieve adsorption equilibrium.

Determination of Desorption Equilibration Time
The test item was identified as having reached desorption equilibrium rapidly in the presence of all soil types.

Adsorption Coefficients
The distribution coefficient (Kd) and the organic carbon normalized adsorption coefficient (Koc) at adsorption equilibrium were determined for five different soil types, at 25 ± 2 ºC.
Overall Kd range: 0.439 to 77.8 cm^3/g
Overall Koc range: 32.4 to 310 cm^3/g
log10 Koc range: 1.51 to 2.49

Desorption Coefficients
The apparent desorption coefficient (Kdes) and the organic carbon normalized apparent desorption coefficient (Kdes (oc)) at desorption equilibrium were determined for five different soil types at 25 ± 2 ºC.
Overall Kdes range: 2.10 to 106 cm^3/g
Overall Kdes (oc) range: 105 to 422 cm^3/g
log10 Kdes (oc) range: 2.02 to 2.62

Adsorption Isotherms
The Freundlich adsorption coefficient at adsorption equilibrium, art 25 ± 2 °C, has been determined for five soil types. The results are summarized in the following table:
Soil Type* Freundlich Adsorption Coefficient K (µg^1-1/n (cm^3)^1/n g^-1) Freundlich Exponent 1/n r^2 Organic Carbon Normalized Adsorption Coefficient, K (µg^1-1/n (cm^3)1/n g^-1)
2 2.75 0.854 0.993 105
3 1.59 0.916 1.000 36.3
4 3.18 0.948 0.999 82.9
5 0.537 0.916 0.999 47.9
7 80.6 0.862 0.999 322

Desorption IsothermsThe Freundlich desorption coefficient at desorption equilibrium and 25 ± 2 °C has been determined for five soil types. The results are summarized in the following table:
Soil Type* Freundlich Desorption Coefficient K des/F (µg^1-1/n (cm^3)^1/n g^-1) Freundlich Exponent 1/n r^2 Organic Carbon Normalized Desorption Coefficient, K des/F(oc) (µg^1-1/n (cm3)^1/n g^-1)
2 0.415 0.973 0.995 15.9
3 0.360 0.986 1.000 8.23
4 0.336 1.05 0.998 8.75
5 0.307 0.974 0.999 27.4
7 17.1 0.993 0.999 68.3
Executive summary:

The adsorption and desorption behaviour of FRET 15-0735 has been determined with soils of differing pH, organic carbon content and textural classification,using a batch equilibrium method. The experimental procedures were designed to be compatible withMethod 106 of the OECD Guidelines for Testing of Chemicals, 21 January 2000. 

Adsorption Coefficients. The distribution coefficient (Kd) and organic carbon normalized adsorption coefficient (Koc) were determined at adsorption equilibrium, for five different soil types, at 25 ± 2°C.

Overall Kdrange:      0.439 to 77.8 cm3/g

Overall Kocrange:     32.4 to 310 cm3/g       log10Kocrange:         1.51 to 2.49

           

Desorption Coefficients. The mean apparent desorption coefficient (Kdes) and organic carbon normalized desorption coefficient (Kdes (oc)) were determined at desorption equilibrium, for five different soil types, at 25 ± 2°C.

Overall Kdesrange:     2.10 to 106cm3/g
Overall Kdes (oc)range: 105 to 422 cm3/g     log10Kdes (oc)range: 2.02 to 2.62

 

Description of key information

The adsorption and desorption behaviour of FRET 15-0735 has been determined with soils of differing pH, organic carbon content and textural classification,using a batch equilibrium method. The experimental procedures were designed to be compatible with Method 106 of the OECD Guidelines for Testing of Chemicals, 21 January 2000. 

Adsorption Coefficients. The distribution coefficient (Kd) and organic carbon normalized adsorption coefficient (Koc) were determined at adsorption equilibrium, for five different soil types, at 25 ± 2°C.

Overall Kdrange:      0.439 to 77.8 cm3/g

Overall Kocrange:     32.4 to 310 cm3/g       log10Kocrange:         1.51 to 2.49

           

Desorption Coefficients. The mean apparent desorption coefficient (Kdes) and organic carbon normalized desorption coefficient (Kdes (oc)) were determined at desorption equilibrium, for five different soil types, at 25 ± 2°C.

Overall Kdesrange:     2.10 to 106cm3/g
Overall Kdes (oc)range: 105 to 422 cm3/g     log10Kdes (oc)range: 2.02 to 2.62

Key value for chemical safety assessment

Koc at 20 °C:
310

Additional information