ethametsulfuron-methyl (ISO); methyl 2-[(4-ethoxy-6-methylamino-1,3,5-triazin-2-yl)carbamoylsulfamoyl]benzoate

Adsorption / desorption

Administrative data

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: U.S. EPA Pesticide Assessment Guidelines, Subdivision N, 163-1 (1982)

Deviations:

no

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil

Test material

Test material information

Constituent 1

Reference substance name:

Reference substance 002

Cas Number:

97780-06-8

Test material form:

solid

Details on test material:

Purity: 85-99%

Specific details on test material used for the study:

Radiochemical purity: 97.1%; Specific activity: 39.55 µCi/mg

Radiolabelling:

yes

Remarks:

phenyl label

Study design

Test temperature:

20 ± 2°C

Batch equilibrium or other method

Analytical monitoring:

yes

Matrix properties

Matrix properties 1

Matrix no.:

#1

Matrix type:

clay loam

% Clay:

32

% Silt:

48

% Sand:

20

% Org. carbon:

2.9

pH:

6.4

CEC:

27.2 meq/100 g soil d.w.

Bulk density (g/cm³):

1.1

Matrix properties 2

Matrix no.:

#2

Matrix type:

loam

% Clay:

12

% Silt:

46

% Sand:

42

% Org. carbon:

0.5

pH:

8.2

CEC:

11.2 meq/100 g soil d.w.

Bulk density (g/cm³):

1.09

Matrix properties 3

Matrix no.:

#3

Matrix type:

sandy loam

% Clay:

14

% Silt:

32

% Sand:

54

% Org. carbon:

1.4

pH:

7.7

CEC:

9.2 meq/100 g soil d.w.

Bulk density (g/cm³):

1.12

Matrix properties 4

Matrix no.:

#4

Matrix type:

silty clay

% Clay:

44

% Silt:

44

% Sand:

12

% Org. carbon:

1.8

pH:

7.6

CEC:

19.1 meq/100 g soil d.w.

Bulk density (g/cm³):

1.06

Matrix properties 5

Matrix no.:

#5

Matrix type:

sandy loam

% Clay:

9

% Silt:

24

% Sand:

67

% Org. carbon:

1.2

pH:

5.7

CEC:

6.1 meq/100 g soil d.w.

Bulk density (g/cm³):

1.22

Duration of adsorption equilibration

Duration:

24 h

Initial conc. measured:

>= 0.003 - <= 0.3 other: µg/mL

Temp.:

>= 18 - <= 22 °C

Remarks:

For all the samples

Duration of desorption equilibration

Duration:

24 h

Conc. of adsorbed test mat.:

0.3 other: µg/mL

Temp.:

20 °C

Remarks:

For all the samples

Results and discussion

Adsorption coefficient

Adsorption coefficient 1

Key result

Sample No.:

#1

Type:

Kd

Value:

19.37 other: mL/g

Matrix:

Clay loam

% Org. carbon:

2.9

Adsorption coefficient 2

Key result

Sample No.:

#2

Type:

Kd

Value:

0.22 other: mL/g

Matrix:

Loam

% Org. carbon:

0.5

Adsorption coefficient 3

Key result

Sample No.:

#3

Type:

Kd

Value:

0.56 other: mL/g

Matrix:

Sandy loam

% Org. carbon:

1.4

Adsorption coefficient 4

Key result

Sample No.:

#4

Type:

Kd

Value:

0.83 other: mL/g

Matrix:

Silty clay

% Org. carbon:

1.8

Adsorption coefficient 5

Key result

Sample No.:

#5

Type:

Kd

Value:

3.66 other: mL/g

Matrix:

Sandy loam

% Org. carbon:

1.2

Adsorption coefficient 6

Key result

Sample No.:

#1

Type:

Koc

Value:

667.9 other: mL/g

Matrix:

Clay Loam

Adsorption coefficient 7

Key result

Sample No.:

#2

Type:

Koc

Value:

44.6 other: mL/g

Matrix:

Loam

Adsorption coefficient 8

Key result

Sample No.:

#3

Type:

Koc

Value:

39.7 other: mL/g

Matrix:

Sandy Loam

Adsorption coefficient 9

Key result

Sample No.:

#4

Type:

Koc

Value:

45.9 other: mL/g

Matrix:

Silty Clay

Adsorption coefficient 10

Key result

Sample No.:

#5

Type:

Koc

Value:

305.2 other: mL/g

Matrix:

Sandy Loam

Results: Batch equilibrium or other method

Recovery of test material:

The average material balance ranged from 97.2 to 107.9% and is within the acceptable guideline range of 90-110% of the applied radioactivity.

Mass balance (%) at end of desorption phase

Mass balance (%) at end of desorption phase 1

Sample no.:

#1

Duration:

24 h

% Desorption:

107.9

Mass balance (%) at end of desorption phase 2

Sample no.:

#2

Duration:

24 h

% Desorption:

107.1

Mass balance (%) at end of desorption phase 3

Sample no.:

#3

Duration:

24 h

% Desorption:

101.6

Mass balance (%) at end of desorption phase 4

Sample no.:

#4

Duration:

24 h

% Desorption:

97.2

Mass balance (%) at end of desorption phase 5

Sample no.:

#5

Duration:

24 h

% Desorption:

104.1

Transformation products:

no

Applicant's summary and conclusion

Conclusions:

Average sorption coefficient
Kd: 4.93 mL/g
Kom: 129.0 mL/g
Koc: 220.7 mL/g

Total percent of test item desorbed after both desorption intervals (DT):
Drummer soil: 31.9%
Porterville soil: 39.9%
Nambsheim soil: 44.4%
Lleida soil: 39.4%
Sassafras soil: 82.8%

Executive summary:

The adsorption and desorption properties of the test substance in five different soils was investigated in the laboratory using 14C-test substance according to the procedures outlined in U.S. EPA Pesticide Assessment Guidelines, Subdivision N, 163-1 and OECD Guideline for the Testing of Chemicals, OECD 106 (January 2000). The adsorption coefficients Kd, Kom, and Koc, and the Freundlich adsorption isotherm parameters KF, KFom, KFoc and 1/n were calculated for Drummer, Porterville (California), Lleida, Nambsheim and Sassafras #16 soils.

The texture of the soils included a clay loam (Drummer), a loam (Porterville or California), two sandy loams (Nambsheim and Sassafras #16) and a silty clay (Lleida). The percent organic matter (Walkley-Black method) of the soils ranged from 0.9-5.0% and the pH in 0.01 M CaCl2 ranged from 5.0-7.9.

Adsorption experiment was performed using the batch equilibration method on the soils with five nominal test concentrations (0.003, 0.015, 0.03, 0.15 and 0.3 µg/mL) of the test item prepared in 0.01 M CaCl2. Two desorption cycles were performed on samples treated at the highest test concentration.

A 1:1, 1:5, or 1:10 (w/v) soil-to-solution ratio was used in the definitive testing. The sorption coefficients Kd, Kom and Koc were calculated for each soil at each concentration of the test item. A summary of the average sorption coefficients for each soil is given in the table below:

SOIL	Kd(mL/g)	Kom(mL/g)	Koc(mL/g)
Drummer	19.37	387.4	667.9
Porterville	0.22	24.8	44.6
Nambsheim	0.56	23.2	39.7
Lleida	0.83	26.6	45.9
Sassafras #16	3.66	183.1	305.2
Average	4.93	129.0	220.7

The values for the Freundlich adsorption isotherm parameter KF, KFom, KFoc, and 1/n were derived from the linear form of the Freundlich equation for all soils. A summary of the adsorption isotherm parameters for each soil is given in the table below:

SOIL	KF	KFOM	KFOC	1/n	R2
Drummer	10.66842	213.368	367.877	0.8697	0.9998
Porterville	0.19774	21.971	39.548	0.9754	0.9804
Nambsheim	0.36000	15.000	25.714	0.8879	0.9985
Lleida	0.74114	23.908	41.174	0.9771	0.9837
Sassafras # 16	1.46994	73.497	122.495	0.7827	0.9837
Average	2.68745	69.549	119.362	0.8986	0.9892

The percent 14C-test substance desorbed from the soils during two desorption intervals (D1 and D2) was calculated and totalled (DT) for all soils at the highest test solution concentration. The DT values ranged from 31.9% in the Drummer soil to 44.4% in the Nambsheim soil. In general, lower desorption values were observed in second desorption interval for all soils. The lowest desorption was observed in Drummer and Porterville soils in the first and second desorption interval, respectively whereas, the highest desorption was observed in Sassafras #16 soils in both desorption intervals (D1 and D2). A summary of the average percent desorption for each soil is given in the table below:

SOIL	D1(%)	D2(%)	DT(%)
Drummer	16.0	15.9	31.9
Porterville	24.5	15.5	39.9
Nambsheim	25.5	18.9	44.4
Lleida	24.0	15.4	39.4
Sassafras # 16	58.3	24.5	82.8