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Environmental fate & pathways

Adsorption / desorption

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Endpoint:
adsorption / desorption: screening
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
The rationale to read across the data is attached in section 13.
Reason / purpose:
read-across source
Type:
Koc
Value:
92 other: mL/kg
Temp.:
20 °C
% Org. carbon:
1.87
Remarks on result:
other: KFoc in Speyer 2.2 soil, 1/n 0.82, r^2 0.982, 10 datapoints
Type:
Koc
Value:
567 other: mL/kg
Temp.:
20 °C
% Org. carbon:
0.94
Remarks on result:
other: KFoc in Speyer 2.3 soil, 1/n 0.64, r^2 0.991, 10 datapoints
Type:
Koc
Value:
979 other: mL/kg
Temp.:
20 °C
% Org. carbon:
1.64
Remarks on result:
other: KFoc in Speyer 6S soil, 1/n 0.78, r^2 0.99, 10 datapoints
Type:
Koc
Value:
546 other: mL/kg
Temp.:
20 °C
Remarks on result:
other: Mean KFoc, 1/n 0.75
Concentration of test substance at end of adsorption equilibration period:
Analysed concentration in the liquid phase after 48 h (adsorption kinetics):
Speyer 2.2 soil: 6.99 mg/L
Speyer 2.3 soil: 4.36 mg/L
Speyer 6S soil: 5.42 mg/L
Details on results (Batch equilibrium method):
Determination of equilibrium time (adsorption kinetics):
The graphs show a rapid increase of the adsorption of TMAC to all the soils in the first 3 hours of contact time. After 3 hours contact time equilibration was reached. No TMAC was detected in the blank samples.

Determination of adsorption isotherms:
Adsorption isotherms could be described by the Freundlich equation. The fits of the Freundlich adsorption isotherms to the data are shown bellow in the field "any other information on results incl. tables".

The pH of the supernatants after 48 h (adsorption kinetics) was 5.6 for Speyer 2.2 soil and 7.0 for Speyer 2.3 and Speyer 6S soil.

At the end of the isotherm experiment, the pH was 5.6-6.0 for Speyer 2.2 soil, 7.0-7.1 for Speyer 2.3 and 6.9-7.1 for Speyer 6S soil.

Table: Koc and Kd values of TMAC determined during adsorption kinetics test at an initial nominal concentration of 10 mg/L

pe

Value

Temperature

% Org. carbon

Remarks

Koc

44

20 °C

1.87

Speyer 2.2 (Loamy sand)-48 h

Kd

0.8

20 °C

1.87

Speyer 2.2 (Loamy sand)-48 h

Koc

270

20 °C

0.94

Speyer 2.3 (Sandy loam)-48 h

Kd

2.5

20 °C

0.94

Speyer 2.3 (Sandy loam)-48 h

Koc

525

20 °C

1.64

Speyer 6S (Clay)-48 h

Kd

8.6

20 °C

1.64

Speyer 6S (Clay)-48 h

Validity criteria fulfilled:
yes
Conclusions:
The adsorption behavior of TMAC was studied in three different soils, including a loamy sand (Speyer 2.2 soil; %oc 1.87), a sandy loam (Speyer 2.3 soil; %oc 0.94) and a clay soil (Speyer 6S soil; %oc 1.64). The adsorption behavior of TMAC was studied in three different soils, including a loamy sand (Speyer 2.2 soil; %oc 1.87), a sandy loam (Speyer 2.3 soil; %oc 0.94) and a clay soil (Speyer 6S soil; %oc 1.64). Adsorption isotherms were determined over a TMAC concentration range of 0.25 - 25 mg/L and a contact time of 24 hours. TMAC adsorption isotherms could be described by the Freundlich equation.
The KFoc value of TMAC was 92 (1/n 0.82), 567 (1/n 0.64) and 979 (1/n 0.78) in three different soils (mean KFoc 546, 1/n 0.75). This result is read across to MTBAC.
Endpoint:
adsorption / desorption: screening
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
The rationale to read across the data is attached in section 13.
Reason / purpose:
read-across source
Media:
soil
Type:
Koc
Value:
87.3 other: mL/kg
Temp.:
20 °C
% Org. carbon:
1.87
Remarks on result:
other: KFoc in Speyer 2.2 soil, 1/n 0.84, r^2 0.9981, 10 datapoints
Type:
Koc
Value:
585 other: mL/kg
Temp.:
20 °C
% Org. carbon:
0.94
Remarks on result:
other: KFoc in Speyer 2.3 soil, 1/n 0.64, r^2 0.9988, 10 datapoints
Type:
Koc
Value:
1 017 other: mL/kg
Temp.:
20 °C
% Org. carbon:
1.64
Remarks on result:
other: KFoc in Speyer 6S soil, 1/n 0.77, r^2 0.9975, 10 datapoints
Type:
Koc
Value:
563 other: mL/kg
Temp.:
20 °C
Remarks on result:
other: Mean KFoc, 1/n 0.75
Concentration of test substance at end of adsorption equilibration period:
Analysed concentration in the liquid phase after 48 h (adsorption kinetics):
Speyer 2.2 soil: 7.46 mg/L
Speyer 2.3 soil: 4.62 mg/L
Speyer 6S soil: 5.77 mg/L
Details on results (Batch equilibrium method):
Determination of equilibrium time (adsorption kinetics):
The graphs show a rapid increase of the adsorption of TMAH pentahydrate to all the soils in the first 3 hours of contact time. After 24 hours contact time equilibration was reached. No TMAH pentahydrate was detected in the blank samples.

Determination of adsorption isotherms:
Adsorption isotherms could be described by the Freundlich equation. The fits of the Freundlich adsorption isotherms to the data are shown bellow in the field "any other information on results incl. tables".

The pH of the supernatants after 48 h (adsorption kinetics) was 5.6 for Speyer 2.2 soil and 7.0 for Speyer 2.3 and Speyer 6S soil.

At the end of the isotherm experiment, the pH was 5.6-5.7 for Speyer 2.2 soil, 7.0 for Speyer 2.3 and Speyer 6S soil.

Table: Koc and Kd values of TMAH pentahydrate determined during adsorption kinetics test at an initial nominal concentration of 10 mg/L

Type

Value

Temperature

% Org. carbon

Remarks

Koc

35

20 °C

1.87

Speyer 2.2 (Loamy sand)-48 h

Kd

0.7

20 °C

1.87

Speyer 2.2 (Loamy sand)-48 h

Koc

258

20 °C

0.94

Speyer 2.3 (Sandy loam)-48 h

Kd

2.4

20 °C

0.94

Speyer 2.3 (Sandy loam)-48 h

Koc

452

20 °C

1.64

Speyer 6S (Clay)-48 h

Kd

7.4

20 °C

1.64

Speyer 6S (Clay)-48 h

 

Validity criteria fulfilled:
yes
Conclusions:
The adsorption behavior of TMAH pentahydrate was studied in three different soils, including a loamy sand (Speyer 2.2 soil; %oc 1.87), a sandy loam (Speyer 2.3 soil; %oc 0.94) and a clay soil (Speyer 6S soil; %oc 1.64). The KFoc value of TMAH pentahydrate was 87 (1/n 0.84), 585 (1/n 0.64) and 1017 (1/n 0.77) in three different soils (mean KFoc 563, 1/n 0.75). This result is read across to MTBAC.

Description of key information

The KFoc of MTBAC was derived in a weight-of-evidence approach, in part through read-across from substances TMAH pentahydrate and TMAC. The KFoc values of these substances were determined in three different soils, in accordance with OECD guideline 106 and GLP (see read-across justification in IUCLID section 13).
The KFoc value of TMAH pentahydrate was 87 (1/n 0.84), 585 (1/n 0.64) and 1017 (1/n 0.77) in the three different soils tested (mean KFoc 563, 1/n 0.75).
The KFoc value of TMAC was 92 (1/n 0.82), 567 (1/n 0.64) and 979 (1/n 0.78) in the three different soils tested (mean KFoc 546, 1/n 0.75).
The mean KFoc value of TMAH and TMAC was 555 (1/n 0.75).

Key value for chemical safety assessment

Koc at 20 °C:
555

Additional information

The adsorption behaviour of MTBAC was estimated based on two relevant studies available for structural analogues TMAH pentahydrate and TMAC.

The mean KFoc value of TMAH and TMAC was 555 (1/n 0.75)

Brands (2013a,b) carried out OECD106 studies with TMAH pentahydrate and TMAC which can be regarded as representative for the tetramethylammonium cation. For both read-across substances a rapid increase of adsorption to soil was observed. Adsorption plateaus were reached in all tested soils after 3 or 24 hours for TMAC and TMAH pentahydrate, respectively. The mean KFoc values (for 3 tested soil types) were 563 and 546 for TMAH pentahydrate and TMAC, respectively. The fact that these values do not differ significantly indicates that the different anions (hydroxide and chloride) did not influence the adsorption. The results of both studies can be used for the calculation of a mean KFoc value in a weight of evidence approach, because the substances have a similar structure as MTBAC (see read-across report in section 13 for further justification).