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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
15 August 2012 - 25 July 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted in accordance with current Guideline and GLP compliant
Qualifier:
according to
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Deviations:
no
GLP compliance:
yes
Type of method:
batch equilibrium method
Media:
soil
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Water solubility: 1.6 mg/L in water at 25°C
- log Pow: 4.1 at 25°C
- Stability of test material at room temperature: Stable
Radiolabelling:
no
Test temperature:
20 ± 2°C
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 1.000, 0.500, 0.102, 0.051 and 0.010 µg a.i./mL
- Sampling interval: 48h adsorption, 24h desorption
- Sample storage before analysis: Analysed immediately, final solutions stored at 4°C before analysis
Details on matrix:
MARSILLARGUES COLLECTION AND STORAGE
- Geographic location: Syngenta Agro SAS, La Paluzette, F-34590 Marsillargues, France
- Sampling depth (cm): 3-10
- Storage conditions: ambient
- Date of Collection: 07 June 2011
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): Sieved (2mm) and air dried

PROPERTIES
- Soil texture: Silty clay
- % sand: 6
- % silt: 56
- % clay: 39
- Soil taxonomic classification: Entisols, Aquents
- pH: 8.1 (water); 7.83 (0.01M CaCl2)
- Organic carbon (%): 1.2
- CEC (meq/100 g): 12.2
- Moisture at 1/3 atm (%): 29.3

18 ACRES COLLECTION AND STORAGE
- Geographic location: Jealott's Hill Farm, Nupton Road, Warfield, Bracknell, UK
- Sampling depth (cm): 5-20
- Storage conditions: ambient
- Date of Collection: 08 June 2011
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): Sieved (2mm) and air dried

PROPERTIES
- Soil texture: Sandy Clay Loam
- % sand: 51
- % silt: 24
- % clay: 25
- Soil taxonomic classification: Alfisols, Aqualf
- pH: 6.1 (water); 5.47 (0.01M CaCl2)
- Organic carbon (%): 2.4
- CEC (meq/100 g): 18.9
- Moisture at 1/3 atm (%): 23.6

GARTNECKER COLLECTION AND STORAGE
- Geographic location: Syngenta Crop Protection AG, Les Barges, Switzerland
- Sampling depth (cm): 5-20
- Storage conditions: ambient
- Date of Collection: 31 May 2011
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): Sieved (2mm) and air dried

PROPERTIES
- Soil texture: Loam
- % sand: 45
- % silt: 43
- % clay: 12
- Soil taxonomic classification: Entisols, Fluvents
- pH: 7.7 (water); 7.14 (0.01M CaCl2)
- Organic carbon (%): 2.2
- CEC (meq/100 g): 10.8
- Moisture at 1/3 atm (%): 28.8

NORTH DAKOTA COLLECTION AND STORAGE
- Geographic location: Gardner, North Dakota (Cass County) USA
- Sampling depth (cm): Not Supplied
- Storage conditions: ambient
- Date of Collection: 13 June 2011
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): Sieved (2mm) and air dried

PROPERTIES
- Soil texture: Sandy Clay Loam
- % sand: 63
- % silt: 14
- % clay: 23
- Soil taxonomic classification: Typic Argiabolboll
- pH: 7.8 (water); 7.06 (0.01M CaCl2)
- Organic carbon (%): 2.5
- CEC (meq/100 g): 29.3
- Moisture at 1/3 atm (%): 23.6

MADERA COLLECTION AND STORAGE
- Geographic location: Madera, California (Madera County) USA
- Sampling depth (cm): Not Supplied
- Storage conditions: ambient
- Date of Collection: 20 June 2011
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): Sieved (2mm) and air dried

PROPERTIES
- Soil texture: Loamy sand
- % sand: 87
- % silt: 7
- % clay: 6
- Soil taxonomic classification: Fluvaquentic Haploxerolls
- pH: 7.0 (water); 6.56 (0.01M CaCl2)
- Organic carbon (%): 0.4
- CEC (meq/100 g): 7.3
- Moisture at 1/10 atm (%): 15.3
Details on test conditions:
TEST CONDITIONS
- Buffer: 0.01M Calcium Chloride solution
- pH:
Marsillargues = 7.81-7.84
18 Acres = 5.41-5.53
Gartenacker = 7.12-7.15
North Dakota = 7.05-7.06
Madera = 6.49-6.62
Suspended solids concentration: Solids > 0.2 µm removed by centrifugation


TEST SYSTEM
- Type, size and further details on reaction vessel: 50mL polyethylene tubes
- Water filtered (i.e. yes/no; type of size of filter used, if any): 0.01 M CaCl2 solution made with filtered Milli-Q water
- Amount of soil and water per treatment (if simulation test): 2g soil (dry weight); 36 mL CaCl2 solution; 4 mL test item solution
- Soil-water ratio (if simulation test): 1:20 (soil:solution)
- Number of reaction vessels/concentration: 2 (+1 control)
- Measuring equipment:
- Test performed in closed vessels: Yes
- Method of preparation of test solution: Stock test solution prepared in acetonitrile. Serial dilutions of this gave test solutions in 0.01M CaCl2 at required concentrations for spiking into vessels (10, 5, 1, 0.5 and 0.1 µg/mL). Acetonitrile content in final test solution ≤0.1% v/v.
- Are the residues from the adsorption phase used for desorption: Fresh 0.01 M CaCl2 used, original soil pellet re-used
Sample No.:
#1
Duration:
48 h
Initial conc. measured:
>= 0.2 - <= 20 mg/kg soil d.w.
Sample No.:
#2
Duration:
48 h
Initial conc. measured:
>= 0.2 - <= 20 mg/kg soil d.w.
Sample No.:
#3
Duration:
48 h
Initial conc. measured:
>= 0.2 - <= 20 mg/kg soil d.w.
Sample No.:
#4
Duration:
48 h
Initial conc. measured:
>= 0.2 - <= 20 mg/kg soil d.w.
Sample No.:
#5
Duration:
48 h
Initial conc. measured:
>= 0.2 - <= 20 mg/kg soil d.w.
Sample no.:
#1
Duration:
24 h
Conc. of adsorbed test mat.:
0.104 mg/kg soil d.w.
Sample no.:
#2
Duration:
24 h
Conc. of adsorbed test mat.:
0.134 mg/kg soil d.w.
Sample no.:
#3
Duration:
24 h
Conc. of adsorbed test mat.:
0.126 mg/kg soil d.w.
Sample no.:
#4
Duration:
24 h
Conc. of adsorbed test mat.:
0.139 mg/kg soil d.w.
Sample no.:
#5
Duration:
24 h
Conc. of adsorbed test mat.:
0.078 mg/kg soil d.w.
Type:
Kd
Value:
>= 16.85 - <= 26.33
Temp.:
20 °C
% Org. carbon:
ca. 1.2
Remarks on result:
other: Marsillargues
Type:
Koc
Value:
>= 1 404 - <= 2 194
Temp.:
20 °C
% Org. carbon:
ca. 1.2
Remarks on result:
other: Marsillargues
Type:
Kd
Value:
>= 31.78 - <= 40.52
Temp.:
20 °C
% Org. carbon:
ca. 2.4
Remarks on result:
other: 18 Acres
Type:
Koc
Value:
>= 1 324 - <= 1 688
Temp.:
20 °C
% Org. carbon:
ca. 2.4
Remarks on result:
other: 18 Acres
Type:
Kd
Value:
>= 26.07 - <= 32.01
Temp.:
20 °C
% Org. carbon:
ca. 2.2
Remarks on result:
other: Gartenacker
Type:
Koc
Value:
>= 1 185 - <= 1 455
Temp.:
20 °C
% Org. carbon:
ca. 2.2
Remarks on result:
other: Gartenacker
Type:
Kd
Value:
>= 32.53 - <= 42.15
Temp.:
20 °C
% Org. carbon:
ca. 2.5
Remarks on result:
other: North Dakota
Type:
Koc
Value:
>= 1 301 - <= 1 686
Temp.:
20 °C
% Org. carbon:
ca. 2.5
Remarks on result:
other: North Dakota
Type:
Kd
Value:
>= 9.86 - <= 14.27
Temp.:
20 °C
% Org. carbon:
ca. 0.4
Remarks on result:
other: Madera
Type:
Koc
Value:
>= 2 462 - <= 3 568
Temp.:
20 °C
% Org. carbon:
ca. 0.4
Remarks on result:
other: Madera
Adsorption and desorption constants:
See Tables 7 & 8 of report
Recovery of test material:
See Table 9 of Report (Mass Balance)
Concentration of test substance at end of adsorption equilibration period:
See Tables 2-6 of report. Amount on sorbent residue is calculated by difference (total applied - concentration in solution)
Concentration of test substance at end of desorption equilibration period:
See Tables 2-6 of report. Amount on sorbent residue is calculated by difference (total applied - concentration in solution)
Sample no.:
#1
Duration:
24 h
% Desorption:
ca. 86.6
Sample no.:
#2
Duration:
24 h
% Desorption:
ca. 85.5
Sample no.:
#3
Duration:
24 h
% Desorption:
ca. 81.4
Sample no.:
#4
Duration:
24 h
% Desorption:
>= 72.9 - <= 87
Sample no.:
#5
Duration:
24 h
% Desorption:
ca. 82.7
Transformation products:
not measured
Details on results (Batch equilibrium method):
PRELIMINARY TEST
- Sample purity: 99.4%
- Weighed soil: 2 g
- Volume of CaCl2 solution: 2 mL, 10 mL, or 40 mL
- Initial test substance concentration: 1 µg/mL
- Test substance concentration in final solution: 0.1 µg/mL


MAIN TEST: PERFORMANCE
- Test material stability during adsorption/desorption phase: Stable
- Experimental conditions maintained throughout the study: Yes
- Buffer/test substance interactions affecting sorption: No
- Further chemical interactions: No
- Buffer-catalyzed degradation of test substance: No
- Anomalies or problems encountered (if yes): No

RESIDUES
- Extractable residues (% of applied amount at end of study period): 72.9-87.0%
- Non-extractable residues (% of applied amount at end of study period): 13.0-27.1%
Validity criteria fulfilled:
yes
Conclusions:
The adsorption and desorption properties of the test item were studied in five different soils: Marsillargues (Silty clay; France), 18 Acres (Sandy clay loam; UK), Gartenacker (Loam; Switzerland), North Dakota (Sandy clay loam; USA) and Madera (Loamy sand; USA).

Using the McCall Classification scale (Reference 2) to assess a chemical’s potential mobility in soil (based on its KFOC), the test item can be classified as having a “low” potential mobility in Marsillargues, 18 Acres, Gartenacker and North Dakota soils and a “slight” potential mobility in Madera soil.

Calculated Mass Balances ranged from 72.9 to 87.0% for North Dakota soil and ranged from 81.4 to 86.6% for other soils.

The Mass Balance data obtained confirmed that the test item was stable in the test system for at least the duration of the definitive isotherm test.
Executive summary:

The adsorption/desorption characteristics of the test item were studied in 5 different soils: Marsillargues (Silty clay; France), 18 Acres (Sandy clay loam; UK), Gartenacker (Loam; Switzerland), North Dakota (Sandy clay loam; USA) and Madera (Loamy sand; USA) using a standard batch equilibrium method, in the dark at 20°C. The chemical was added to soil:aqueous slurries (resulting in a final nominal composition of 1 g of soil: 20 mL aqueous 0.01 M CaCl2 for all soils) to achieve five nominal rates of application (0.01, 0.05, 0.1, 0.5 and 1.0 μg/mL). The soil adsorption coefficients Kd and KOC, together with the Freundlich adsorption constants KF and KFOC, were determined for each soil.

The adsorption phase was followed by a single desorption phase to determine the reversibility of adsorption.

Following preliminary tests, an adsorption equilibration time of 48 hours and a desorption equilibration period of 24 hours were selected for the definitive test. Recovery of the applied test item concentration was determined, at all concentrations for each soil type, by LC/MSMS analysis of the adsorption and desorption supernatants. Mass Balances were determined at one concentration (0.1 μg/mL) for each soil type and at all definitive test concentrations for the soil with the highest Kd value (North Dakota soil).

For all soils the recovery of the test item was quantitative. Mass Balances ranged from 72.9 to 87.0% for North Dakota soil and ranged from 81.4 to 86.6% for other soils. The calculated Freundlich coefficients (KF) for adsorption ranged from 11.59 to 33.23 g/g, while the 1/n values for adsorption ranged from 0.95 to 1.00. When corrected for the organic matter content of the soils, the resultant KFOC values for adsorption ranged from 1238 to 2896 g/g. The partition coefficients Kd for adsorption ranged from 11.38 to 36.89 g/g with the corresponding KOC for adsorption ranging from 1314 to 2845 g/g. These data indicated that the test item ranged from having low mobility to having slight mobility in the soils studied. A summary of the key values is shown below.

 

Parameter

Marsillargues

18 Acres

Gartenacker

North Dakota

Madera

Texture

Silty clay

Sandy clay loam

Loam

Sandy clay loam

Loamy sand

pH (0.01 M CaCl2)

7.49

6.17

7.10

7.10

6.67

%OC

1.2

2.4

2.2

2.5

0.4

Adsorption

KF

18.13

31.33

27.24

33.23

11.59

KFOC

1511

1305

1238

1329

2896

1/n

0.95

0.96

0.98

0.97

1.00

r2

0.99

0.99

1.00

1.00

0.99

Kd (averaged)

21.42

35.55

28.90

36.89

11.38

KOC(averaged)

1785

1481

1314

1476

2845

Desorption

KF

25.40

34.51

38.44

39.06

26.33

KFOC

2117

1438

1747

1562

6582

1/n

0.96

0.95

0.97

0.96

1.05

r2

0.99

1.00

1.00

1.00

0.99

Kd (averaged)

29.67

42.01

42.45

45.05

22.16

KOC(averaged)

2473

1751

1930

1802

5539

 

The desorption constants of the test item were higher than the adsorption constants thus demonstrating that adsorption was not fully reversible.

Description of key information

Using the McCall Classification scale to assess a chemical’s potential mobility in soil (based on its KFOC), the test item can be classified as having a “low” potential mobility in Marsillargues, 18 Acres, Gartenacker and North Dakota soils and a “slight” potential mobility in Madera soil.

Key value for chemical safety assessment

Additional information