Tall oil, maleated

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:

Initiation: September 24, 2013 Completion May 20, 2014

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 (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

no

Test temperature:

Preliminary study: 21.4 °C – 22.5 °C
Tier 2 - Adsorption Kinetics at One Concentration of the Test Substance 21.4 °C – 22.5 °C

Analytical monitoring:

yes

Details on sampling:

At each time point the sample jars were removed from the incubator and approximately 14 mL of liquid was transferred to a 15 mL Falcon tube. The tubes were centrifuged at 2500 rpm for 10 minutes. A 10 mL sample of each supernatant was removed by pipette into a 20 mL glass vial. The remainder of the sample in the Falcon tube was added back to the incubation jar.

Matrix no.:

#3

Matrix type:

loam

% Clay:

16

% Silt:

42

% Sand:

42

% Org. carbon:

2.4

pH:

7.5

CEC:

17.3 meq/100 g soil d.w.

Matrix no.:

#5

Matrix type:

sandy loam

% Clay:

14

% Silt:

14

% Sand:

72

% Org. carbon:

1.5

pH:

7.5

CEC:

6.83 meq/100 g soil d.w.

Matrix no.:

#6

Matrix type:

clay

% Clay:

60

% Silt:

39

% Sand:

1

% Org. carbon:

3.3

pH:

7.6

CEC:

32.8 meq/100 g soil d.w.

Matrix no.:

#7

Matrix type:

other: griFood Laboratories, Guelph, Ontario indicated that soils with high organic content are not sieved, therefore there is no value for clay content nor did they render a soil texture for this soil.

% Clay:

0

% Silt:

0

% Sand:

0

% Org. carbon:

43.1

pH:

6.8

CEC:

99.61 meq/100 g soil d.w.

Matrix no.:

#4

Matrix type:

loam

% Clay:

18

% Silt:

31

% Sand:

46

% Org. carbon:

3.5

pH:

7.5

CEC:

16.91 meq/100 g soil d.w.

Details on matrix:

Six soils were collected from various locations in Ontario, Canada, including two locations from a site in Hamilton, two sites in Oakville, one site in Lambton County and one site in the Holland Marsh. The soils include a range of organic carbon and clay contents. They are generally neutral to very slightly basic, reflecting the local nature of Ontario soils.
The soils were collected from the surface down to a depth no greater than 20 cm as specified. They were air dried, gently crushed as needed, and sieved to 2 mm.
Soil Type 4 is a mixture of 96-41-5 and 96-41-4 in a ratio of 5 to 95 so the Clay Content is a calculated value based on the measured values of the two soils used to make soil 87-231-1.

Details on test conditions:

Adsorption kinetics test
A soil/solution ratio of 1:10 was used for this part of the experiment. Equilibrium was achieved in 24 hours (as determined in Tier 1). Each soil was run in duplicate. A blank soil (OECD soil type 5) and a control (test substance with no soil) were also run. Samples were collected and analysed at 2, 6, 24 and 48 hours. The percent adsorption was calculated at each time point and was plotted against time. The distribution coefficient, Kd, was calculated from data obtained.
Desorption kinetics
The soils from the adsorption kinetics experiments which generated a Kd value (Soil types 4 and 7) were used. After equilibration in the presence of test item during the adsorption phase, the aqueous phase was removed and an equal volume of fresh 0.01M CaCl2 was added. The mixture was agitated on an orbital shaker at room temperature (80 rpm) until desorption equilibrium was reached. Samples were serially collected at 6, 24, 48 and 72 hours and analyzed as described above. All incubations were conducted in duplicate and the results were blank corrected. The percent desorption was determined from the concentration of test substance appearing in the aqueous phase, as described in OECD 106.
Adsorption/Desorption isotherms
Five test concentrations (4.81, 14.82, 25.93, 37.03 and 48.13 μg/ml) were used using a soil/solution of 1/10. Soil types 4 and 7 were used as they were the only soils from which a reliable Kd value was obtained in Tier 2. Sacrificial samples (parallel method) were prepared containing 2.7 g (wet weight) soil in a final volume of about 27.0 mL. Incubations were conducted in 50 mL glass centrifuge tubes. The samples were agitated at 80 rpm and the aqueous phase was sampled after 24 hours of incubation. The equilibrium concentrations were determined in solution and the amount adsorbed was calculated.

Sample No.:

#4

Type:

Kd

Value:

2.21 other: cm3/g

% Org. carbon:

3.5

Sample No.:

#4

Type:

Koc

Value:

63 other: cm3/g

Temp.:

22 °C

% Org. carbon:

3.5

Sample No.:

#7

Type:

Kd

Value:

385.8 other: cm3/g

% Org. carbon:

43.1

Sample No.:

#7

Type:

Koc

Value:

895.1 other: cm3/g

Temp.:

22 °C

% Org. carbon:

43.1

Adsorption and desorption constants:

The results showed a wide range of Kd values ranging from no adsorption (Soil types 3, 5 and 6) to a high adsorptivity (Soil type 7). There is a very loose association between the Kd and the organic content of the soil. Soils with less than 3.5% organic content did not adsorb the test item to any significant degree.
It can be concluded from the desorption experiments that the desorption comes to equilibrium after 48 hours, with a net adsorption to soil types 4 and 7. The adsorption is therefore not reversible for these soil types.
Freundlich Adsorption Isotherm Data:
KF-ads (μg1-1/n(cm3)1/ng-1)
94.3 (soil type #4)
20.1 (soil type #7)
Freundlich Desorption Data
KF-des (μg1-1/n(cm3)1/ng-1)
161.3 (soil type #4)
no desorption was detected for soil type #7

Validity criteria fulfilled:

yes

Conclusions:

These studies demonstrated that the test item was strongly adsorbed to soils with a high organic content (for example soil type 7) and only weakly adsorbed to soils with less than 3% organic content.
The desorption kinetic study conducted with soil types 4 and 7 loaded with test item in Tier 2, showed that no material was desorbed during the subsequent incubation. This was confirmed during the desorption isotherm studies. Based on these observations and the criteria described in section 79 of OECD 106 (<75% desorption at twice the adsorption incubation time represents irreversible adsorption), we conclude that adsorption of the test item is essentially not reversible.
The behaviour of the test item when interacting with soils is consistent with its chemical structure, as it is an organic solvent (e.g. methanol and dichloromethane) soluble material with surface active groups (fatty acids). The solubility characteristics in the presence of calcium chloride, required in OECD 106, is also entirely consistent with the relative insolubility of the calcium salts of fatty acids.

Executive summary:

The adsorption/desorption study was conducted on test item EnvaMul 600 according to test method OECD 106.

A preliminary test, an adsorption kinetic test, a desorption kinetic test and the determination of Freundlich absorption and desorption isotherms were conducted.

These studies demonstrated that the test item was strongly adsorbed to soils with a high organic content (for example soil type 7) and only weakly adsorbed to soils with less than 3% organic content.

The desorption kinetic study conducted with soil types 4 and 7 loaded with test item in Tier 2, showed that no material was desorbed during the subsequent incubation. This was confirmed during the desorption isotherm studies. Based on these observations and the criteria described in section 79 of OECD 106 (<75% desorption at twice the adsorption incubation time represents irreversible adsorption), we conclude that adsorption of the test item is essentially not reversible.

The behaviour of the test item when interacting with soils is consistent with its chemical structure, as it is an organic solvent (e.g. methanol and dichloromethane) soluble material with surface active groups (fatty acids). The solubility characteristics in the presence of calcium chloride, required in OECD 106, is also entirely consistent with the relative insolubility of the calcium salts of fatty acids.

Description of key information

Koc soil # 4 (loam): 63.0 cm3/g (Temperature between 21.4 °C - 22.5 °C)

Koc soil # 7 (loamy sand): 895.1 cm3/g (temperature between 21.4 °C - 22.5 °C)

Key value for chemical safety assessment

Koc at 20 °C:

895.1

Additional information

These studies demonstrated that the test item was strongly adsorbed to soils with a high organic content (for example soil type 7) and only weakly adsorbed to soils with less than 3% organic content.

The desorption kinetic study conducted with soil types 4 and 7 loaded with test item in Tier 2, showed that no material was desorbed during the subsequent incubation. This was confirmed during the desorption isotherm studies.

Based on these observations and the criteria described in section 79 of OECD 106 (<75% desorption at twice the adsorption incubation time represents irreversible adsorption), we conclude that adsorption of the test item is essentially not reversible.

The behavior of the test item when interacting with soils is consistent with its chemical structure, as it is an organic solvent (e.g. methanol and dichloromethane) soluble material with surface active groups (fatty acids). The solubility characteristics in the presence of calcium chloride, required in OECD 106, is also entirely consistent with the relative insolubility of the calcium salts of fatty acids.