Orthosulfamuron

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2000

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

Test material:
[14C-U-phenyl]IR5878 Lot 182
Specific radioactivity: 342008 dpm/µg
154.06 µCi/mg
5.70 MBq/mg
Radiochemical purity: > 97 % (by TLC)

Radiolabelling:

yes

Test temperature:

20C

Details on sampling:

In the Preliminary test each soil sample was incubated at the test substance concentration of 5.014 g/mL for 10 and 30 min, and 1, 2, 4, 8, 16 hours.
The Advanced test was carried out with four test substance concentrations for each soil sample: 5.112 g/mL, 1.066 g/mL, 0.207 g/mL and 0.046 g/mL. For each soil and each concentration, duplicate samples were prepared.

Matrix no.:

#1

Matrix type:

sandy loam

% Clay:

ca. 5.7

% Silt:

ca. 32.3

% Sand:

ca. 62

% Org. carbon:

ca. 1.33

pH:

ca. 6.29

CEC:

ca. 7.65 meq/100 g soil d.w.

Matrix no.:

#2

Matrix type:

silt loam

% Clay:

ca. 17.3

% Silt:

ca. 54.4

% Sand:

ca. 28.3

% Org. carbon:

ca. 2.03

pH:

ca. 5.71

CEC:

ca. 12.17 meq/100 g soil d.w.

Matrix no.:

#3

Matrix type:

silt loam

% Clay:

ca. 8.7

% Silt:

ca. 54.3

% Sand:

ca. 37

% Org. carbon:

ca. 1

pH:

ca. 6.78

CEC:

ca. 10.7 meq/100 g soil d.w.

Matrix no.:

#4

Matrix type:

clay loam

% Clay:

ca. 29

% Silt:

ca. 46.7

% Sand:

ca. 24.3

% Org. carbon:

ca. 2.3

pH:

ca. 7.98

CEC:

ca. 20.06 meq/100 g soil d.w.

Details on matrix:

Method:
The adsorption-desorption of 14C-IR5878 was determined on four different fully characterised soils, according to OECD guideline 106. Tested soils were sandy loam (B-1), silt loam (G-2), silt loam (M-2) and clay loam (VM-1). The characteristics are summarised in Table 7.4-1.

Table 7.4-1 Characteristics of soils
B-1 G-2 M-2 VM-1
Particle size distribution 50-2000 µm (sand) 62.0 28.3 37.0 24.3
2-50 µm (silt) 32.3 54.4 54.3 46.7
< 2 µm (clay) 5.7 17.3 8.7 29.0
USDA classification sandy loam silt loam silt loam clay loam
pH (0.01 M CaCl2) 6.29 5.71 6.78 7.98
Organic carbon (%) 1.33 2.03 1.00 2.30
Cation Exchange capacity (meq / 100 g) 7.65 12.17 10.70 20.06

Details on test conditions:

The study was divided into two parts, according to SETAC and OECD Guidelines, both performed at 20°C: a Preliminary test, to assess the equilibrium time for the adsorption and to check the stability of IR5878 during the adsorption step, and an Advanced test, to obtain adsorption isotherms to be compared with the Freundlich equation.
1-g aliquots of air dried soil samples were re-equilibrated in 0.01 M CaCl2 aqueous solution by stirring the soil suspension for 24 hours at 20°C.
In the Preliminary test each soil sample was incubated at the test substance concentration of 5.014 g/mL for 10 and 30 min, and 1, 2, 4, 8, 16 hours.
The Advanced test was carried out with four test substance concentrations for each soil sample: 5.112 g/mL, 1.066 g/mL, 0.207 g/mL and 0.046 g/mL. For each soil and each concentration, duplicate samples were prepared.
Radioactivity was determined by LSC. Extracts were analysed by TLC and the distribution of radiolabelled compounds quantitated by a Bio-Imaging Analyser.

Sample No.:

#1

Duration:

2 h

Initial conc. measured:

ca. 5.014 other: ug/mL

Temp.:

ca. 20 °C

Sample No.:

#2

Duration:

2 h

Initial conc. measured:

ca. 5.014 other: ug/mL

Temp.:

ca. 20 °C

Sample No.:

#3

Duration:

2 h

Initial conc. measured:

ca. 5.014 other: ug/mL

Temp.:

ca. 20 °C

Sample No.:

#4

Duration:

2 h

Initial conc. measured:

ca. 5.014 other: ug/mL

Temp.:

ca. 20 °C

Computational methods:

The data of adsorption isotherms fitted very well (r2 > 0.97) with Freundlich equation.

Key result

Sample No.:

#1

Type:

Koc

Value:

ca. 283 other: mL/g

Temp.:

20 °C

Matrix:

Sandy loam

% Org. carbon:

ca. 1.33

Key result

Sample No.:

#2

Type:

Koc

Value:

ca. 328 other: mL/g

Temp.:

20 °C

Matrix:

Silt loam

% Org. carbon:

ca. 2.03

Key result

Sample No.:

#3

Type:

Koc

Value:

ca. 550 other: mL/g

Temp.:

20 °C

Matrix:

Silt loam

% Org. carbon:

ca. 1

Key result

Sample No.:

#4

Type:

Koc

Value:

ca. 249 other: other

Temp.:

20 °C

Matrix:

Clay loam

% Org. carbon:

ca. 2.3

Sample No.:

#1

Phase system:

solids-water in soil

Type:

other: Kd

Value:

> 2.337 - < 10.457 other: mL/g

Sample No.:

#2

Phase system:

solids-water in soil

Type:

other: Kd

Value:

> 5.458 - < 11 other: mL/g

Sample No.:

#3

Phase system:

solids-water in soil

Type:

other: Kd

Value:

> 4.941 - < 7.393 other: mL/g

Sample No.:

#4

Phase system:

solids-water in soil

Type:

other: Kd

Value:

> 5.497 - < 6.978 other: mL/g

Adsorption and desorption constants:

Preliminary test showed that:
- the time necessary to reach adsorption equilibrium was 2 hours for all the tested soils;
- four cycles of desorption were necessary to find negligible amounts to be released;
- IR5878 was substantially stable during the adsorption step.

Recovery of test material:

Advanced test: based on the results of the Preliminary test, the incubation time was 2 hours for all the tested soils. The amount of adsorbed IR5878 was 43.35%, 54.09%, 46.63% and 46.51% as percentage mean value respectively in B-1, G-2, M-2 and VM-1 soil. At the end of the desorption cycles, the amount of desorbed IR5878 was 50.35%, 51.20%, 39.21% and 73.70% as percentage mean value respectively in B-1, G-2, M-2 and VM-1 soil.

Transformation products:

not specified

Details on results (Batch equilibrium method):

1-g aliquots of air dried soil samples were re-equilibrated in 0.01 M CaCl2 aqueous solution by stirring the soil suspension for 24 hours at 20°C.
In the Preliminary test each soil sample was incubated at the test substance concentration of 5.014 g/mL for 10 and 30 min, and 1, 2, 4, 8, 16 hours.
The Advanced test was carried out with four test substance concentrations for each soil sample: 5.112 g/mL, 1.066 g/mL, 0.207 g/mL and 0.046 g/mL. For each soil and each concentration, duplicate samples were prepared.
Radioactivity was determined by LSC. Extracts were analysed by TLC and the distribution of radiolabelled compounds quantitated by a Bio-Imaging Analyser.

Findings
Preliminary test showed that:
- the time necessary to reach adsorption equilibrium was 2 hours for all the tested soils;
- four cycles of desorption were necessary to find negligible amounts to be released;
- IR5878 was substantially stable during the adsorption step.
Advanced test: based on the results of the Preliminary test, the incubation time was 2 hours for all the tested soils. The amount of adsorbed IR5878 was 43.35%, 54.09%, 46.63% and 46.51% as percentage mean value respectively in B-1, G-2, M-2 and VM-1 soil. At the end of the desorption cycles, the amount of desorbed IR5878 was 50.35%, 51.20%, 39.21% and 73.70% as percentage mean value respectively in B-1, G-2, M-2 and VM-1 soil.

The data of adsorption isotherms fitted very well (r2 > 0.97) with Freundlich equation. The results of the Advanced test are summarised in Table 7.4-3.

Table 7.4-1     Characteristics of soils

		B-1	G-2	M-2	VM-1
Particle size distribution	50-2000 µm (sand)	62.0	28.3	37.0	24.3
	2-50 µm (silt)	32.3	54.4	54.3	46.7
	< 2 µm (clay)	5.7	17.3	8.7	29.0
USDA classification		sandy loam	silt loam	silt loam	clay loam
pH (CaCl2)		6.29	5.71	6.78	7.98
Organic carbon (%)		1.33	2.03	1.00	2.30
Cation Exchange capacity (meq /)		7.65	12.17	10.70	20.06

  Table 7.4-2     Adsorbed and desorbed IR5878

Soil	Characteristics	Adsorbed IR5878 (% mean value)	Desorbed IR5878 (% mean value)
B-1	sandy loam	43.35	50.35
G-2	silt loam	54.09	51.20
M-2	silt loam	46.63	39.21
VM-1	clay loam	46.51	73.70

  Table 7.4-3     Partition coefficient Kd and Freundlich parameters of adsorption isotherms

Soil	Characteristics	Kd (mean value) (mL/g)	1/N	K’ (or Kf) (mL/g)	Organic carbon (%)	K’oc(mL/g)
B-1	sandy loam	6.003	0.749	3.763	1.33	283
G-2	silt loam	8.568	0.861	6.662	2.03	328
M-2	silt loam	6.251	0.920	5.499	1.00	550
VM-1	clay loam	6.105	0.956	5.725	2.30	249

 

Validity criteria fulfilled:

yes

Conclusions:

The adsorption-desorption study with 14C-IR5878 was carried out in four different soils.
The calculated Koc were 283, 328, 550 and 249, for sandy loam, silt loam, silt loam and clay loam soils, respectively.

Executive summary:

Preliminary test showed that:

-         the time necessary to reach adsorption equilibrium was 2 hours for all the tested soils;

-         four cycles of desorption were necessary to find negligible amounts to be released;

-         IR5878 was substantially stable during the adsorption step.

Advanced test: based on the results of the Preliminary test, the incubation time was 2 hours for all the tested soils. The amount of adsorbed IR5878 was 43.35%, 54.09%, 46.63% and 46.51% as percentage mean value respectively in B-1, G-2, M-2 and VM-1 soil. At the end of the desorption cycles, the amount of desorbed IR5878 was 50.35%, 51.20%, 39.21% and 73.70% as percentage mean value respectively in B-1, G-2, M-2 and VM-1 soil.

The data of adsorption isotherms fitted very well (r²> 0.97) with Freundlich equation. Mass balance was ≥ 93%.

The adsorption-desorption study with¹⁴C-IR5878 was carried out in four different soils.The calculated K_ocwere 283, 328, 550 and 249, for sandy loam, silt loam, silt loam and clay loam soils, respectively

Description of key information

Preliminary test showed that:

-         the time necessary to reach adsorption equilibrium was 2 hours for all the tested soils;

-         four cycles of desorption were necessary to find negligible amounts to be released;

-         IR5878 was substantially stable during the adsorption step.

Advanced test: based on the results of the Preliminary test, the incubation time was 2 hours for all the tested soils. The amount of adsorbed IR5878 was 43.35%, 54.09%, 46.63% and 46.51% as percentage mean value respectively in B-1, G-2, M-2 and VM-1 soil. At the end of the desorption cycles, the amount of desorbed IR5878 was 50.35%, 51.20%, 39.21% and 73.70% as percentage mean value respectively in B-1, G-2, M-2 and VM-1 soil.

The data of adsorption isotherms fitted very well (r²> 0.97) with Freundlich equation. Mass balance was ≥ 93%.

The adsorption-desorption study with¹⁴C-IR5878 was carried out in four different soils.The calculated K_ocwere 283, 328, 550 and 249, for sandy loam, silt loam, silt loam and clay loam soils, respectively

Key value for chemical safety assessment

Koc at 20 °C:

353