1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

28 Jun 1988 to 30 Jun 1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: Environmental Protection Agency (EPA) Pesticide Assessment Guidelines , Subdivision N , Section 163-1

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

25 ºC

Analytical monitoring:

yes

Details on sampling:

See 'Details on test conditions'

Matrix no.:

#1

Matrix type:

sand

% Clay:

2

% Silt:

1

% Sand:

97

% Org. carbon:

0.17

pH:

5.4

CEC:

1.1 meq/100 g soil d.w.

Bulk density (g/cm³):

1.59

Matrix no.:

#2

Matrix type:

silt loam

% Clay:

13

% Silt:

58

% Sand:

29

% Org. carbon:

0.64

pH:

7

CEC:

13 meq/100 g soil d.w.

Bulk density (g/cm³):

1.18

Matrix no.:

#3

Matrix type:

sandy loam

% Clay:

6

% Silt:

31

% Sand:

63

% Org. carbon:

1.16

pH:

7.5

CEC:

23 meq/100 g soil d.w.

Bulk density (g/cm³):

1.42

Matrix no.:

#4

Matrix type:

silty clay loam

% Clay:

28.4

% Silt:

50.2

% Sand:

21.4

% Org. carbon:

1.45

pH:

6.8

CEC:

14.7 meq/100 g soil d.w.

Bulk density (g/cm³):

1.21

Matrix no.:

#5

Matrix type:

clay loam

% Clay:

40

% Silt:

53

% Sand:

7

% Org. carbon:

0.81

pH:

7.8

CEC:

27 meq/100 g soil d.w.

Bulk density (g/cm³):

1.24

Details on matrix:

- Soil: The study was conducted with the following soil types: Plainfield sand (Adams County, Wisconsin), Mississippi silt loam (Greenville, Mississippi), California sandy loam (Tulare County, California), Hagerstown silty clay loam (Frederick County, Maryland), and Arizona silty clay loam (Yuma County, Arizona). Before use, the soils were air-dried and passed through a 2 mm sieve. Physical analysis was performed. Field moisture capacity and bulk density were measured as well. Physical characteristics of the soils are summarized in Table 1 in 'Any other information on materials and methods incl. tables'.

Details on test conditions:

PRELIMINARY STUDIES
- Preliminary studies were conducted to determine the solubility, stability, and potential adsorption to glassware of 14C-substance in aqueous 0.01M Ca(NO3)2. A preliminary study was also conducted to determine an appropriate soil: solution ratio and the adsorption equilibrium time of 14C-substance in aqueous 0.01M Ca(NO3)2 at a target concentration of 10.0 µg/mL on the soil selected for study .
- Preparation of Test Material Solution: A 10.1 µg/mL test material solution was prepared by combining radiolabeled substance (dissolved in ACN) and nonradio labeled substance (dissolved in ACN) at a ratio of 1:9 in aqueous 0.01M Ca(N03)2. The radioactivity concentration of the solution was determined by LSC analysis of duplicate aliquots. The total substance concentration was determined from the mean of the LSC results and the calculated specific activity of the test material in solution (12,218 dpm/µg).
- Solubility of Test Material: Approximately 2- , 10-, and 20-fold dilutions of the 10.1 µg/mL test material solution were prepared for verification of the solubility of 14C-substance in aqueous 0.01 M Ca(N03)2. The solution concentration of 14C-substance was determined by LSC analysis of duplicate aliquots. The total substance (radiolabeled and nonradio labeled) solution concentration was determined from the mean of the LSC results and the calculated specific activity of 14C-substance in the 10.1 µg/ mL test material solution (12,218 dpm/µg). The applied concentrations (0.500, 1.00, 5.00 , and 10.0 µg/mL) versus individual experimental concentrations of the test substance (0.512, 0.511, 0.97, 0.97, 5.15, 5.24, 10.1, and 10.0 µg/ mL) were analyzed by linear regression.
- Stability of Test Material: An aliquot of the 10.1 µg/mL solution of 14C-substance was allowed to stand at room temperature under yellow fluorescent lighting for approximately 24 hours. The radiopurity of 14C-substance in solution was determined by TLC and compared with the original radiopurity determined by the Sponsor.
- Adsorption to Glass: Ten milliliters of the 0.512 µg/mL test material solution were placed in each of 10 glass culture tubes. The 10 samples were placed in a shaker at approximately 25 ºC. Two tubes per sample interval were removed after approximately 1, 2, 5, 8, and 24 hours of equilibration. Duplicate 1.0 mL aliquots from each tube were analyzed by LSC. The solution radioactivity at each interval was compared with the solution radioactivity at Hour 0.
- Adsorption Equilibration Time: Forty samples (10 per soil type) were prepared in glass culture tubes by adding 10 mL of the 10.1 µg/mL test material solution to 2g of soil (Plainfield sand, Mississippi silt loam, California sandy loam, and Hagerstown silty clay loam). The tubes were capped and placed in a shaker at approximately 25ºC. At approximately 1, 2, 5, 8 and 24 hours, duplicate samples of each soil type were removed from the shaker and centrifuged. Duplicate 1.0 mL aliquots of the supernatant were removed and analyzed by LSC to determine the concentration of 14C-substance in solution. The mean percentage of 14C-substance adsorption to soil versus time was plotted for each soil type. The plotted data were used to determine the equilibrium time of the 14C-substance adsorption to soil and the soil: solution ratio used in the definitive study.

DEFINITIVE STUDY
- Preparation of Test Material Solutions: A 10.0 µg/mL solution was prepared by combining radiolabeled test substance (dissolved in ACN) and nonradio labeled test substance (dissolved in ACN) at a ratio of 1:9 in aqueous 0.01M Ca(N03)2. Three dilutions of the 10.0 µg/mL solution were prepared to obtain concentrations of 0.496, 1.01, and 5.01 µg/mL. The radioactivity concentration of each solution was determined by LSC analysis of duplicate aliquots. The total substance concentration was determined from the mean of the LSC results and the calculated specific activity of the test material in solution (11,964 dpm/ µg).
- Adsorption of Test Material to Glass: Since adsorption to glass was observed for the 0.512 µg/mL solution in the preliminary study, duplicate aliquots of each test material solution (10.0, 5.01, 1.01, and 0.496 µg/ml) were placed in glass culture tubes (eight tubes total). The eight samples were placed in a shaking water bath kept at approximately 25 ºC. After 24 hours of equilibration, the tubes were removed. Duplicate 1.0 mL aliquots from each tube were analyzed by LSC. The solution radioactivity at Hour 24 equilibration was compared with that at Hour 0.
- Adsorption of Test Material to Soil: Forty samples (two samples/soil type/ test material concentration) were prepared in glass culture tubes by adding 10.0 mL of the 0.496-, 1.01-, 5.01-, or 10.0-µg/mL test material solutions to an aliquot (approximately 2 g) of Plainfield sand, Mississippi silt loam, California sandy loam, Hagerstown silty clay loam, or Arizona silty clay loam. The tubes were capped and placed in a shaker at approximately 25 ºC. After approximately 24 hours, the samples were removed from the shaker and centrifuged. A measured volume (7.0 mL) of supernatant was removed and duplicate 1.0 mL aliquots were analyzed by LSC. The LSC data were used to calculate the soil and solution concentrations and the percentage of 14C-substance adsorption to soil.
- Desorption of Test Material from Soil: After completion of the adsorption phase, 7 mL of fresh, unfortified aqueous 0.01M Ca(NCO3)2 was added to each sample container to reestablish the 10.0 mL solution volume. The tubes were capped and placed in the shaking water bath at approximately 25 ºC. After approximately 24 hours, the samples were removed from the shaker and centrifuged. Duplicate 1.0 mL aliquots were analyzed by LSC. The LSC data were used to calculate the concentrations and the percentage of 14C-substance desorption from soil.

Duration:

24 h

Temp.:

25 °C

Remarks:

Definitive study: Adsorption of Test Material to Glass - no soil used

Duration:

24 h

Temp.:

25 °C

Remarks:

Definitive study: Adsorption of Test Material to Soil: 40 samples (two samples/soil type/ test material concentration)

Key result

Sample No.:

#1

Type:

Koc

Value:

685 L/kg

pH:

5.4

Temp.:

25 °C

Matrix:

Sand

% Org. carbon:

0.17

Remarks on result:

other: Definitive study results

Key result

Sample No.:

#2

Type:

Koc

Value:

436 L/kg

pH:

7

Temp.:

25 °C

Matrix:

Silt loam

% Org. carbon:

0.64

Remarks on result:

other: Definitive study results

Key result

Sample No.:

#3

Type:

Koc

Value:

382 L/kg

pH:

7.5

Temp.:

25 °C

Matrix:

Sandy loam

% Org. carbon:

1.16

Remarks on result:

other: Definitive study results

Key result

Sample No.:

#4

Type:

Koc

Value:

604 L/kg

pH:

6.8

Temp.:

25 °C

Matrix:

Silty clay

% Org. carbon:

1.45

Remarks on result:

other: Definitive study results

Key result

Sample No.:

#5

Type:

Koc

Value:

1 134 L/kg

pH:

7.8

Temp.:

25 °C

Matrix:

Silty clay loam

% Org. carbon:

0.81

Remarks on result:

other: Definitive study results

Sample No.:

#1

Phase system:

solids-water in soil

Type:

other: Koc - desorption coefficient

Value:

893 L/kg

Temp.:

25 °C

pH:

5.4

Matrix:

Sand

% Org. carbon:

0.17

Remarks on result:

other: Definitive study results

Sample No.:

#2

Phase system:

solids-water in soil

Type:

other: Koc - desorption coefficient

Value:

464 L/kg

Temp.:

25 °C

pH:

7

Matrix:

Silt loam

% Org. carbon:

0.64

Remarks on result:

other: Definitive study results

Sample No.:

#3

Phase system:

solids-water in soil

Type:

other: Koc - desorption coefficient

Value:

455 L/kg

Temp.:

25 °C

pH:

7.5

Matrix:

Sandy loam

% Org. carbon:

1.16

Remarks on result:

other: Definitive study results

Sample No.:

#4

Phase system:

solids-water in soil

Type:

other: Koc - desorption coefficient

Value:

703 L/kg

Temp.:

25 °C

pH:

6.8

Matrix:

Silty clay

% Org. carbon:

1.45

Remarks on result:

other: Definitive study results

Sample No.:

#5

Phase system:

solids-water in soil

Type:

other: Koc - desorption coefficient

Value:

1 229 L/kg

Temp.:

25 °C

pH:

7.8

Matrix:

Silty clay loam

% Org. carbon:

0.81

Remarks on result:

other: Definitive study results

Adsorption and desorption constants:

The adsorption and desorption equilibrium constants are presented in Table 1 in 'Any other information on results incl. tables'.

Recovery of test material:

Not specified

Remarks on result:

not measured/tested

Remarks on result:

not measured/tested

Transformation products:

not specified

Details on results (Batch equilibrium method):

PRELIMINARY STUDIES
- Solubility of Test Material: Radiolabeled test substance was soluble in aqueous 0.01 M Ca(NO3)2 at all concentrations tested. Linear regression analysis demonstrated that the plot of applied concentration versus experimental concentration was linear with a y- intercept of 0.020, a slope of 1.00, and a correlation coefficient of 0.999.
- Adsorption of Test Material to Glass: The mean percentage of 14C-substance adsorbed to glass ranged from 5.4% (Hours 8 and 24) to 7.2% (Hour 5). No correction for adsorption to glass was made to the adsorption data.
- Adsorption Equilibrium. The adsorption of 14C-substance to soil after 1 hour of equilibration was 9.9% (Plainfield sand), 21.5% (Mississippi silt loam), 29.3% (California sandy loam), and 47.1% (Hagerstown silty clay loam). The percent adsorption after 24 hours was 11.2%, 26.5%, 37.3%, and 56.4% for Plainfield sand, Mississippi silt loam, California sandy loam, and Hagerstown silty clay loam, respectively. Since the increase in adsorption over the 8- to 24 - hour period was very small for each soil, the test system was considered to be at equilibrium at 24 hours. To optimize adsorption for the definitive study, a soil solution ratio of 1: 5 and a 24-hour equilibration period were selected.

DEFINITIVE STUDY
- See Table 1 in 'Any other information on results incl tables'.
- Adsorption to Glass: Adsorption of four concentrations of 14C- substance to glass ranged from 4.7% (5.01 µg/mL solution) to 7.0% (1.01 µg/mL solution). The percentage of 14C-substance adsorption to glass was not influenced by the four concentrations of test material used in this study.
- Adsorption of Test Material to Soil: Adsorption of 14C-substance to soil at four concentrations ranged from 16.2% to 22.7% (Plainfield sand), 31.5% to 40.0% (Mississippi silt loam), 41.5% to 53.7% (California sandy loam), 31.5% to 40.0%, 58.8% to 72.5% (Hagerstown silty clay loam), and 60.7% to 72.1% (Arizona silty clay loam). The percentage of adsorption decreased with increasing test material concentration for all soils tested. Linear regression analysis of the solution and soil log concentrations for four concentrations of 14C-substance after 24 hours of equilibration was linear for all soil types, indicating that the adsorption of 14C-substance followed the Freundlich equation. Correlation coefficients of 0.999 (Plainfield sand), 0.999 (Mississippi silt loam), 0.998 (California sandy loam), 0.999 (Hagerstown silty clay loam), and 0.999 (Arizona silty clay loam) were calculated. The slopes of the regression line (l/n) were 0.895 (Plainfield sand), 0.899 (Mississippi silt loam), 0.894 (California sandy loam), 0.831 (Hagerstown silty clay loam) , and 0.841 (Arizona silty clay loam) (Table 1), respectively. The adsorption values were calculated from the results of the linear regression analysis of the soil and solution log concentrations of 14C-substance. The Kd values were 1.2 (Plainfield sand), 2.81 (Mississippi silt loam), 4.49 (California sandy loam), 8.88 (Hagerstown silty clay loam), and 9.34 (Arizona silty clay loam). The Koc value calculated for each soil was 685 (Plainfield sand), 436 (Mississippi silt loam) , 382 (California sandy loam), 604 (Hagerstown silty clay loam) , and 1,134 (Arizona silty clay loam) (Table 1) .
- Desorption of Test Material from Soil: The percent desorption of 14C-substance from soil after 24 hours ranged from 40.8% to 45.3% (Plainfield sand), 38.2% to 42.2% (Mississippi silt loam), 23.4% to 32.0% (California sandy loam), 14.5% to 22.7% (Hagerstown silty clay loam), and 16.5% to 24.3% (Arizona silty clay loam). The percentage of desorption values decreased with decreasing concentration of test material, except for Plainfield sand, which had approximately constant values. Calculated desorption Kd values were 1.57 (Plainfield sand), 3.00 (Mississippi silt loam), 5.35 (California sandy loam), 10.3 (Hagerstown silty clay loam), and 10.1 (Arizona silty clay loam). The desorption Kd value was greater than the adsorption Kd value for all the soils. Correlation coefficients were 0.998 or greater for all soils. The slopes of the regression line (1/n) ranged from 0.827 (Hagerstown silty clay loam) to 0.926 (Plainfield sand). The Koc values ranged from 455 (California sandy loam) to 893 (Plainfield sand) (Table 1).

Table 1. Linear Regression Analysis of the Adsorption and Desorption Soil and Solution Log Concentrations of Four Concentration of ¹⁴C-substance in Aqueous 0.01M Ca(NO3)2 for Five Soils

Soil	Equilibrium Constant Kd	Slope (1/n)	Correlation Coefficient	Sorption Coefficient (Koc)
Adsorption
Plainfield sand	1.20	0.895	0.999	685
Mississippi silt loam	2.81	0.899	0.999	436
California sandy loam	4.49	0.894	0.998	382
Hagerstown silty clay	8.88	0.831	0.999	604
Arizona silty clay loam	9.34	0.841	0.999	1134
Desorption
Plainfield sand	1.57	0.926	0.998	893
Mississippi silt loam	3.00	0.910	0.999	464
California sandy loam	5.35	0.875	0.999	455
Hagerstown silty clay	0.3	0.827	0.999	703
Arizona silty clay loam	10.1	0.834	0.999	1229

 

Validity criteria fulfilled:

not specified

Conclusions:

Radiolabeled test substance was soluble and stable in aqueous 0.01 M Ca(NO3)2 at the concentrations tested. Adsorption of 14C-substance to glass at 25 ºC was approximately 5% to 7% at all intervals and test material concentrations. Linear regression analysis of the adsorption data demonstrated that the plot of the soil and solution log concentrations of 14C-substance at the concentrations tested was linear for all soil types (correlation coefficient of at least 0.998) indicating that the adsorption of 14C-substance followed the Freundlich equation. The slope (1/n) of the regression line ranged from 0.831 to 0.899 for the soils. The adsorption Kd values were 1.20 (Plainfield sand), 2.81 (Mississippi silt loam), 4.49 (California sandy loam), 8.88 (Hagerstown silty clay loam), and 9.34 (Arizona silty clay loam). The adsorption Koc values were 685 (Plainfield sand), 436 (Mississippi silt loam), 382 (California sandy loam), 604 (Hagerstown silty clay loam), and 1,134 (Arizona silty clay loam). The desorption values were 1.57 (Plainfield sand), 3.00 (Mississippi silt loam), 5.35 (California sandy loam), 10.3 (Hagerstown silty clay loam), and 10.1 (Arizona silty clay loam). The desorption Koc values were 893 (Plainfield sand), 464 (Mississippi clay loam), 455 (California sandy loam), 703 (Hagerstown silty clay loam), and 1,229 (Arizona silty clay loam).

Executive summary:

The adsorption and desorption characteristics of the substance were studied on five representative agricultural soils (Plainfield sand, Mississippi silt loam, California sandy loam, Hagerstown silty clay loam, and Arizona silty clay loam). The study was conducted according to the Environmental Protection Agency Pesticide Assessment Guidelines, Subdivision N, Section 163-1 and in compliance with GLP criteria. Preliminary studies indicated that the radiolabelled test substance in aqueous 0.01 M calcium nitrate [Ca(NO3)2] was soluble and stable at the concentrations tested. Adsorption of the test material to glass ranged from 5.4% (Hours 8 and 24) to 7.2% (Hour 5). A preliminary study of the adsorption of the test material in aqueous 0.01M Ca(NO3)2 to soil was conducted to establish the soil solution ratio (1 : 5) and the equilibration time (24 hours) for the definitive study. Soil - solution samples were prepared for each soil type in 0.496-, 1.01-, 5.01-, and 10.0- µg/mL solutions of test material in aqueous 0.01 M Ca(NO3)2 . The samples were equilibrated for 24 hours at approximately 25 ºC. After centrifugation, the supernatant was analyzed by liquid scintillation counting (LSC) to determine adsorption. Solution removed from each sample for analysis was replaced by an equal volume of unfortified aqueous 0.01M Ca (NO3)2. The samples were equilibrated for 24 hours at approximately 25 ºC and the supernatant was analyzed by LSC to determine desorption. Linear regression analysis of the adsorption data demonstrated that the plot of the soil and solution log concentrations of the radiolabelled test substance at the concentrations tested was linear for all soil types (correlation coefficient of at least 0.998), indicating that the adsorption of the radiolabelled test substance followed the Freundlich equation. The slope (1/n) of the regression line ranged from 0.831 to 0.899 for the soils. The adsorption and desorption equilibrium constant (Kd) and sorption coefficient (Koc) values are summarized here: 

	Adsorption		Desorption
Soil type	Kd	Koc	Kd	Koc
Plainfield sand	1.20	685	1.57	893
Mississippi silt loam	2.81	436	3.00	464
California sandy loam	4.49	382	5.35	455
Hagerstown silty clay loam	8.88	604	10.3	703
Arizona silty clay loam	9.34	1134	10.1	1229

 

Reference 2

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

28 Jun 1988 to 30 Jun 1988

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

Adsorption and desorption of 14C-triazoles labelled test substance was studied at four concentrations between 1 - 10 mg/L in four various soils. One oven-dry soil sample per concentration was shaken over night at 20 °C temperature. In the desorption part of the test soil-water mixtures were shaken for three days. Measurements were made with LSC.

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

20.0 °C

Analytical monitoring:

yes

Details on sampling:

not specified

Details on matrix:

- Soil types: origin and properties of soils used for adsorption and desorption measurements are given in Table 1 in 'Any other information on materials and methods incl tables'.

Details on test conditions:

- Substance standard solution: 100 mg of analytical grade substance containing approx. 5% of 14C-labelled material were dissolved in 100 cm3 of methylene chloride (= 1000 ppm). For adsorption experiments appropriate aqueous dilutions were used (1.0, 2.5, 5.0 and 10.0 ppm).

ADSORPTION STUDIES
- 10 to 50 g of oven-dry soil material was mixed in centrifuge tubes with 100 cm3 of aqueous solutions with concentrations of 1.0 to 10.0 ppm of the substance. The suspensions were shaken overnight on the water bath shaker at a temperature of 20.0 °C. The mixture was then filtered under vacuum through a funnel containing a filter paper and collected in a 100 cm3 measuring cylinder. The tube and the filter cake were washed with exactly the same volume of distilled water which is needed to obtain 100 cm3 in the measuring cylinder. Aliquots of 0.5 cm3 of the filtrate were mixed with 20 cm3 of scintillation solution and the mixtures were submitted to liquid scintillation counting. The equilibrium concentration of the substance in the aqueous solution was then calculated by means of a calibration equation. This equation, in which the number of disintegrations per minute (dpm) is a function of the concentration, was obtained by regression analysis. From the difference between initial and equilibrium concentration the amount of the substance adsorbed onto soil particles was calculated.

DESORPTION STUDIES
- After adsorption, the filtered soil was weighed to determine the amount of water retained and then untreated distilled water was added to obtain a total of 100 cm3. The soil-water mixtures were shaken for 3 days on the water bath shaker at 20.0 °C. After shaking, the suspensions were filtered and 0.5 cm3 of the filtrate subjected to radioassay as described for the adsorption studies. The equilibrium concentration of the substance in the aqueous solution was then calculated.

Remarks:

See 'Details on test conditions'

Duration:

3 d

Temp.:

20 °C

Remarks:

1.0, 2.5, 5.0 and 10.0 ppm

Key result

Sample No.:

#1

Type:

Koc

Remarks:

Freundlich Coefficients

Value:

665 L/kg

pH:

6.7

Temp.:

20 °C

Matrix:

Collombey soil

% Org. carbon:

1.28

Remarks on result:

other: This Koc value was not provided in the original study but was taken from EU Draft Renewal Assessment Report Volume 3 (March 2017).

Key result

Sample No.:

#2

Type:

Koc

Remarks:

Freundlich Coefficients

Value:

1 817 L/kg

pH:

6.7

Temp.:

20 °C

Matrix:

Vetroz soil

% Org. carbon:

3.25

Remarks on result:

other: This Koc value was not provided in the original study but was taken from EU Draft Renewal Assessment Report Volume 3 (March 2017).

Key result

Sample No.:

#3

Type:

Koc

Remarks:

Freundlich Coefficients

Value:

1 255 L/kg

pH:

6.1

Temp.:

20 °C

Matrix:

Les Evouettes soil

% Org. carbon:

2.09

Remarks on result:

other: This Koc value was not provided in the original study but was taken from EU Draft Renewal Assessment Report Volume 3 (March 2017).

Key result

Sample No.:

#4

Type:

Koc

Remarks:

Freundlich Coefficients

Value:

1 575 L/kg

pH:

6.3

Temp.:

20 °C

Matrix:

Lakeland soil

% Org. carbon:

0.7

Remarks on result:

other: This Koc value was not provided in the original study but was taken from EU Draft Renewal Assessment Report Volume 3 (March 2017).

Sample No.:

#1

Type:

other: Adsorption constant

Value:

8.48 other: µg/g soil

pH:

7.8

Temp.:

20 °C

Matrix:

Collombey soil

% Org. carbon:

1.28

Remarks on result:

other: value from original report

Sample No.:

#2

Type:

other: Adsorption constant

Value:

59.03 other: µg/g soil

pH:

6.7

Temp.:

20 °C

Matrix:

Vetroz soil

% Org. carbon:

3.25

Remarks on result:

other: value from original report

Sample No.:

#3

Type:

other: Adsorption constant

Value:

26.2 other: µg/g soil

pH:

6.1

Temp.:

20 °C

Matrix:

Les Evouettes soil

% Org. carbon:

2.09

Remarks on result:

other: value from original report

Sample No.:

#4

Type:

other: Adsorption constant

Value:

10.96 other: µg/g soil

pH:

6.3

Temp.:

20 °C

Matrix:

Lakeland soil

% Org. carbon:

0.7

Remarks on result:

other: value from original report

Sample No.:

#1

Phase system:

solids-water in soil

Type:

other: Freundlich desorption constant

Value:

10.57 other: µg/g soil

Temp.:

20 °C

pH:

7.8

Matrix:

Collombey soil

% Org. carbon:

1.28

Sample No.:

#2

Phase system:

solids-water in soil

Type:

other: Freundlich desorption constant

Value:

70.75 other: µg/g soil

Temp.:

20 °C

pH:

6.7

Matrix:

Vetroz soil

% Org. carbon:

3.25

Sample No.:

#3

Phase system:

solids-water in soil

Type:

other: Freundlich desorption constant

Value:

31.65 other: µg/g soil

Temp.:

20 °C

pH:

6.1

Matrix:

Les Evouttes soil

% Org. carbon:

2.09

Sample No.:

#4

Phase system:

solids-water in soil

Type:

other: Freundlich desorption constant

Value:

15.95 other: µg/g soil

Temp.:

20 °C

pH:

6.3

Matrix:

Lakeland soil

% Org. carbon:

0.7

Adsorption and desorption constants:

The constants are presented in Table 1 in 'Any other information on results incl. tables'

Recovery of test material:

Not specified

Remarks on result:

not measured/tested

Remarks on result:

not measured/tested

Transformation products:

not specified

Details on results (Batch equilibrium method):

ADSORPTION
The results of the adsorption studies were assessed with the aid of the empirical Freundlich adsorption isotherm which may be written.log (x/m) = log k + (1/n) log ce, were x/m is the amount adsorbed by unit mass of adsorbent when in equilibrium with a solution of concentration ce , k and 1/n being constants for the given system and temperature. Logarithmic plots of x/m against c gave a straight line for all soils tested. Values of k, which can be obtained by reading from the graphs the values of x/m at ce= 1 or by calculating the Freundlich equations by regression analysis have been calculated and are summarized in Table 1 in ‘Any other information on results incl tables’. The adsorption constants (k) were found to be between 8.48 and 59.0 µg per g of soil demonstrating that the substance is strongly adsorbed onto soil particles. In Table 1 in ‘Any other information on results incl tables’. the adsorption coefficient was additionally reported as Q-value, expressing the µg of fungicide adsorbed per g of soil organic matter (OM): Q =100 k/OM%. The average Q mass value obtained with the four different soil types was calculated to be 770 µg/g OM. A low mobility in soil of the fungicide has to be expected. The values of 1/n give the slope of the adsorption isotherm and are all less than unity so that the amount of adsorbed fungicide increases less rapidly than the concentration, If 1/n were unity the adsorption equation would be equivalent to the distribution law. However, as an approximation the adsorption constant can be considered a distribution coefficient for soil-water systems.

DESORPTION
- The desorption results obtained with the four soil types are summarized also in Table 1 in 'Any other information on results incl. tables’. The results after a 3 day desorption period show that the slopes of the desorption isotherms were the same as those calculated for the adsorption isotherms. The desorption constants were higher than the adsorption coefficients ranging from 15.95 to 70.95 µg/g of soil. Consequently, the average Q mass value for desorption (988 µg/g OM) exceeded the corresponding value for adsorption demonstrating that the desorption process was not completely reversible after a desorption period of 3 days.

Table 1. Constants from Freundlich adsorption and desorption isotherms for the substance with various soils.

Soil	k	Q	1/n
	[µg/g soil]	[µg/g OM*]
Adsorption
Vetroz	59.03	1054	0.88
Les Evouettes	26.20	728	0.81
Collombey	8.48	385	0.86
Lakeland	10.96	913	0.85
Desorption
Vetroz	70.75	1263	0.86
Les Evouettes	31.65	879	0.79
Collombey	10.57	480	0.85
Lakeland	15.95	1329	0.85

*OM: Organic Matter

Validity criteria fulfilled:

not specified

Conclusions:

The Freundlich adsorption constants (k) determined for the substance varied between 8.48 and 59.0 µg per g of soil demonstrating that the compound was more strongly adsorbed on soil particles than the other pesticides tested. The desorption constants varied between 10.6 and 70.8 µg/g of soil. The actual Koc values were not presented in the original report but were taken from EU Draft Renewal Assessment Report Volume 3 (March 2017).

Executive summary:

Adsorption and desorption of ¹⁴C-triazoles labelled test substance was studied at four concentrations between 1 - 10 mg/L in four various soils. One oven-dry soil sample per concentration was shaken over night at 20 °C temperature. In the desorption part of the test soil-water mixtures were shaken for three days. Measurements were made with LSC. The Freundlich adsorption constants (k) determined for the substance varied between 8.48 and 59.0 µg/g of soil demonstrating that the compound was more strongly adsorbed on soil particles than the other pesticides tested. Desorption occurred at a slower rate than adsorption, and the results show that the adsorption process was not completely reversible after a desorption time of 3 days. The desorption constants varied between 10.6 and 70.8 µg/g of soil. The actual Koc values were not presented in the original report but were taken from EU Draft Renewal Assessment Report Volume 3 (March 2017).

Description of key information

The arithmetic mean Kfoc for the soil adsorption of the substance was determined to be 950 L/kg, EPA 163 -1 (or similar), Saxena 1988 and Burkhard 1980.

Key value for chemical safety assessment

Koc at 20 °C:

950

Additional information

There are two studies available for this endpoint. Both studies used the equilibrium batch method and were selected as key studies. One study followed EPA 163-1 guideline and complied with GLP criteria ( Saxena 1988, Reliability 1). It covered five types of soil. The second study covered four soil types and was performed without following standard guidelines (Burkhard 1980, Reliability 2). It was not specified whether GLP criteria were met. The soil types, test conditions, and results are summarised in the table below. 

Table. Soil adsorption

USDA	Name / Origin	OC*	pH	Kf *	Kfoc*	1/n	Author / Year
Sand	Collombey, CH	1.28	7.8	8.48	665a	0.86	Burkhard / 1980
Sandy clay loam	Vetroz, CH	3.25	6.7	59.03	1817a	0.88	Burkhard / 1980
Loam	Les Evouettes, CH	2.09	6.1	26.2	1255a	0.81	Burkhard / 1980
Sand	Lakeland, US	0.70	6.3	10.96	1575a	0.85	Burkhard / 1980
Sand	Plainfield, US	0.17	5.4	1.20	685	0.90	Saxena / 1988
Silt loam	Mississippi, US	0.64	7.0	2.81	436	0.90	Saxena / 1988
Sandy loam	California, US	1.16	7.5	4.49	382	0.89	Saxena / 1988
Silty clay loam	Hagerstown, US	1.45	6.8	8.88	604	0.83	Saxena / 1988
Silty clay loam	Arizona, US	0.81	7.8	9.34	1134	0.84	Saxena / 1988
Arithmetic mean Kfoc	-	-	-	-	950	-	-

*         Units: OC(%), Kf and Kfoc (mL/g)

a)        Kfoc values not provided in original study report (only Kom). Values taken from EU Draft Renewal Assessment Report Volume 3 (March 2017)