3-iodo-2-propynyl butylcarbamate

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:

1989-08-08 to 1990-10-29

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: U. S. EPA Pesticide Assessment Guidelines Subdivision N, Section 163-1

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Agriculture Canada Trade Memorandum T-1-255

Deviations:

no

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL RADIOLABELED
- Source and lot/batch No.of test material: NBN/l/77/1

RADIOLABELLING INFORMATION
- Specific activity: 108 µCi/mg


SOURCE OF TEST MATERIAL NON-LABELED
- Source and lot/batch No.of test material: N.J. L7-93

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature

Radiolabelling:

yes

Test temperature:

22 +/- 1 °C

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 100, 50 10, 1 µg/mL
- Sampling interval: three desorption steps were performed on those soils receiving the highest concentration

Matrix no.:

#1

Matrix type:

sandy loam

% Clay:

10

% Silt:

24

% Sand:

66

% Org. carbon:

0.75

pH:

6

CEC:

4.9 meq/100 g soil d.w.

Matrix no.:

#2

Matrix type:

sand

% Clay:

4

% Silt:

4

% Sand:

92

% Org. carbon:

0.46

pH:

5.8

CEC:

2 meq/100 g soil d.w.

Matrix no.:

#3

Matrix type:

loam

% Clay:

14

% Silt:

40

% Sand:

46

% Org. carbon:

1.6

pH:

5.9

CEC:

10 meq/100 g soil d.w.

Matrix no.:

#4

Matrix type:

silty clay

% Clay:

40

% Silt:

46

% Sand:

14

% Org. carbon:

1.3

pH:

5.6

CEC:

21.1 meq/100 g soil d.w.

Matrix no.:

#5

Matrix type:

sand

% Clay:

3

% Silt:

5

% Sand:

92

% Org. carbon:

2

pH:

3.9

CEC:

3.5 meq/100 g soil d.w.

Details on matrix:

COLLECTION AND STORAGE
- Soil preparation: 2 mm sieved

Details on test conditions:

TEST CONDITIONS
- initial concentrations: 100, 50, 10, 1 µg/L

TEST SYSTEM
- Type, size and further details on reaction vessel: 50 mL glass centrifuge tubes, capped with Teflon-lined screw caps
- Solution/Soil ratio: 5:1
- Number of reaction vessels/concentration (replicates): 2
- Measuring equipment: HPLC UV and LSC detector
- Test performed in closed vessels: yes

Duration:

2 h

Temp.:

22 °C

Remarks:

for respective concentrations

Duration:

2 h

Temp.:

22 °C

Remarks:

for respective concentrations

Computational methods:

Log-log scales were used to plot the amount of test item adsorbed versus equilibrium concentration in terms of the empirical Freundlich adsorption equation (Weber, 1986):

X/M = K C^N

or in the log transformation form:

log (X/M) = log K + N(log C)

where X is the amount of test item adsorbed (µg), M is the mass of soil (g), C is the equilibrium concentration (µg/mL), and log K and N are constants representing the intercept of the isotherm and the slope, respectively.

Log-log scales also were used to plot the amount of test item adsorbed versus equilibrium mole fraction in a modified Freundlich equation format (Bowman, 1982):

Sy = Kmf * Z^N

or in the log transformation form:

log Sy = log Kmf + N log Z

where Kmf = S at Z = 1.0 and is designated in this fashion to avoid confusion with the K value in the traditional Freundlich isotherm. The K, value is only an empirical regression constant and has no real value as a means of comparing adsorption since it is evaluated Z = 1.0 (pure pesticide). Instead of using K values as a measure of relative adsorption, adsorption values [Sy] are determined at a common Z value within the range of the data, where Y = log Z. This subscript, Y, is a simple way of quickly identifying the log concentration (log mole fraction) at which the relative adsorption comparisons were made.

Key result

Sample No.:

#1

Type:

Koc

Value:

90.1 dimensionless

pH:

6

Temp.:

22 °C

Matrix:

loam

Key result

Sample No.:

#2

Type:

Koc

Value:

309 dimensionless

pH:

5.8

Temp.:

22 °C

Matrix:

sand

Key result

Sample No.:

#3

Type:

Koc

Value:

61 dimensionless

pH:

5.9

Temp.:

22 °C

Matrix:

loam

Key result

Sample No.:

#4

Type:

Koc

Value:

89.2 dimensionless

pH:

5.6

Temp.:

22 °C

Matrix:

clay

Key result

Sample No.:

#5

Type:

Koc

Value:

123 dimensionless

pH:

3.9

Temp.:

22 °C

Matrix:

sand

Adsorption and desorption constants:

Kads: 0.676 - 2.46
Kdes: 3.43 - 31.3

Recovery of test material:

Material balance values ranged from 87.66 to 99.11 % for the soils used.

Duration:

2 h

% Adsorption:

> 7.99 - < 37.9

Transformation products:

not measured

Validity criteria fulfilled:

yes

Conclusions:

The test item was adsorbed in moderate amounts by the soils used in this study with adsorption K values ranging from 61.0 to 309. Test item adsorption did not appear to be highly correlated with soil organic matter content, clay content, or cation exchange capacity. Test item was readily degraded to propargyl butyl carbamate in suspensions from the Evesboro, Blackoar, and Mexico soils. Differences in relative adsorption between soils may have been related to differences in the extent of test item degradation

Executive summary:

The test item adsorption/desorption by soils was investigated using radioisotope techniques via the batch equilibrium (slurry) method (Weber, 1986). The soils used in this study were a Hanford sandy loam (#1), a Centhan sand (#2), a Blackoar loam (#3), a Mexico silty clay (#4), and an Evesboro sand (#5). Initial test item concentrations were approximately 100, 50, 10, and 1 µg/mL, and the solution: soil ratio was 5:1. Three desorption steps were performed on those soils receiving the highest initial test item concentration.Adsorption and desorption isotherms are presented using two sets of units. The first set of data (µg Basis) is presented with amount adsorbed (µg/g) plotted versus equilibrium concentration (µg/mL). Kads and Kdes values were calculated with this data to permit comparison of relative adsorption. The second set of data (mole Basis) is presented with amount adsorbed (mole/g) plotted versus equilibrium mole fraction (unitless). Using this format, relative adsorption values (Sy) are compared at a common solution mole fraction. The subscript Y is a simple means of quickly identifying the log concentration (log mole fraction) at which the relative adsorption comparisons were made. For this study, Y = -6. Test item was adsorbed in moderate amounts by soils with Kads values ranging from 0.676 to 2.46 and S-6 values ranging from 1.45e-07 to 3.01e-08. Test item adsorption did not appear to be directly related to either soil organic matter content, clay content, or cation exchange capacity. Adsorption and desorption K values were variable indicating that factors other than organic carbon content determine the extent of test item adsorption. Bound C residues were quantified using soil oxidation and liquid scintillation techniques. Material balance values ranged from 87.66 to 99.11% further validating adsorption and desorption calculations. 

Description of key information

The test item was adsorbed in moderate amounts by the soils used in this study with adsorption K values ranging from 61.0 to 309. Test item adsorption did not appear to be highly correlated with soil organic matter content, clay content, or cation exchange capacity. Test item was readily degraded to propargyl butyl carbamate in suspensions from the soils. Differences in relative adsorption between soils may have been related to differences in the extent of test item degradation. As a worst case assumption Koc value of 309 is applied as key value.

Key value for chemical safety assessment

Koc at 20 °C:

309

Additional information

The test item adsorption/desorption by soils was investigated using radioisotope techniques via the batch equilibrium (slurry) method (Weber, 1986). The soils used in this study were a Hanford sandy loam (#1), a Centhan sand (#2), a Blackoar loam (#3), a Mexico silty clay (#4), and an Evesboro sand (#5). Initial test item concentrations were approximately 100, 50, 10, and 1 µg/mL, and the solution: soil ratio was 5:1. Three desorption steps were performed on those soils receiving the highest initial test item concentration.Adsorption and desorption isotherms are presented using two sets of units. The first set of data (µg Basis) is presented with amount adsorbed (µg/g) plotted versus equilibrium concentration (µg/mL). Kads and Kdes values were calculated with this data to permit comparison of relative adsorption. The second set of data (mole Basis) is presented with amount adsorbed (mole/g) plotted versus equilibrium mole fraction (unitless). Using this format, relative adsorption values (Sy) are compared at a common solution mole fraction. The subscript Y is a simple means of quickly identifying the log concentration (log mole fraction) at which the relative adsorption comparisons were made. For this study, Y = -6.Test item was adsorbed in moderate amounts by soils with Kads values ranging from 0.676 to 2.46 and S-6 values ranging from 1.45e-07 to 3.01e-08. Test item adsorption did not appear to be directly related to either soil organic matter content, clay content, or cation exchange capacity. Adsorption and desorption K values were variable indicating that factors other than organic carbon content determine the extent of test item adsorption. Bound C residues were quantified using soil oxidation and liquid scintillation techniques. Material balance values ranged from 87.66 to 99.11% further validating adsorption and desorption calculations.