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Environmental fate & pathways

Adsorption / desorption

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Endpoint:
adsorption / desorption: screening
Type of information:
other: handbook
Adequacy of study:
supporting study
Study period:
not reported
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Handbook data for which assurances of quality, such as peer review processes are not reported.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Data presented as a short abstract in a handbook.
GLP compliance:
not specified
Radiolabelling:
not specified
Type:
Kd
Remarks:
All soils (L/kg)
Value:
780
Remarks on result:
other: Minimum 2.4E2 Maximum 3.0E3 s.d. 2.7 compendium of 5 values
Type:
Kd
Remarks:
Mineral (L/kg)
Value:
560
Remarks on result:
other: Minimum 2.4E2 Maximum 1.3E3 s.d. 2.1 compendium of 4 values
Type:
Kd
Remarks:
Organic (L/kg)
Value:
3 000
Remarks on result:
other: Only one value available

Data presented as a short abstract, no further information available.

Validity criteria fulfilled:
not applicable
Conclusions:
The water-soil equilibrium distribution coefficient of tantalum was reported to be:
Kd All soils 7.8E2 (Minimum 2.4E2 Maximum 3.0E3 s.d. 2.7 compendium of 5 values)
Kd Mineral 5.6E2 (Minimum 2.4E2 Maximum 1.3E3 s.d. 2.1 compendium of 4 values)
Kd Organic 3.0E3
Executive summary:

The water-soil equilibrium distribution coefficient of tantalum was reported to be:

Kd All soils 7.8E2 (Minimum 2.4E2 Maximum 3.0E3 s.d. 2.7 compendium of 5 values)

Kd Mineral 5.6E2 (Minimum 2.4E2 Maximum 1.3E3 s.d. 2.1 compendium of 4 values)

Kd Organic 3.0E3

Endpoint:
adsorption / desorption: screening
Data waiving:
study technically not feasible
Justification for data waiving:
other:

Description of key information

In accordance with section 2 of REACH Annex XI, further information on adsorption/desorption, listed under standard information requirement 9.3.3 of Annex IX of the same regulation, does not need to be conducted as a study is technically not feasible to conduct. As tantalum is highly insoluble in water (≤ 21 µg/L), analytical measurements cannot be performed with sufficient accuracy.

Handbook data from the IAEA indicate the following values for Ta:

Kd (All soils) = 7.8E2 L/kg (Minimum 2.4E2 Maximum 3.0E3 s.d. 2.7 compendium of 5 values);

Kd (Mineral) = 5.6E2 L/kg (Minimum 2.4E2 Maximum 1.3E3 s.d. 2.1 compendium of 4 values);

Kd (Organic) = 3.0E3 L/kg, No guideline reported; Kd value from TRS-364.
A mean value, Kd 720 mL/g was carried forward for risk assessment purposes, this is equivalent to a Koc of 36000 based on 2 % OC.

Key value for chemical safety assessment

Koc at 20 °C:
36 000

Other adsorption coefficients

Type:
log Kp (solids-water in soil)
Value in L/kg:
720
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in sediment)
Value in L/kg:
1 800
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in suspended matter)
Value in L/kg:
3 600
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in raw sewage sludge)
Value in L/kg:
10 800
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in settled sewage sludge)
Value in L/kg:
10 800
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in activated sewage sludge)
Value in L/kg:
13 300
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in effluent sewage sludge)
Value in L/kg:
13 300
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (soil-water)
Value in L/kg:
1 080
at the temperature of:
20 °C

Additional information

In accordance with section 2 of REACH Annex XI, the adsorption/desorption screening study does not need to be conducted as the study is technically not feasible to conduct. Due the insolubility of tantalum in water, analytical measurements cannot be performed with sufficient accuracy.


Other adsorption coefficient indicated as dimensionless:
- log Kp (suspended matter-water) ,901.0 at the temperature 20.0°C
- log Kp (sediment-water) ,901.0 at the temperature 20.0°C