Registration Dossier
Registration Dossier
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EC number: 231-166-4 | CAS number: 7440-58-6
Adsorption / desorption
Administrative data
Link to relevant study record(s)
Description of key information
The availability of metal compounds for uptake by biota can differ from site to site and may change over time due to many processes, including weathering and (de)sorption processes. It should also be noted that Kd values are accurate only during an equilibrium state, which is difficult to reach for metals in the environment. As a consequence, part of the metal present in the solid phase may be encapsulated in the mineral fraction and is therefore not available.
Since the partitioning coefficient is such an important parameter that can drive the outcome of the exposure assessment, the assessment of the data quality and relevance of all collected measured Kd-values should be done with care.
The IAEA Technical Reports Series No. 364 ( Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Temperate Environments, 1994) publication reported Kd values for Hf within the range of 1500 to 5400 L/kg, with a Kd of 2500 L/kg for all soils in general.
These values and IAEA assessor were considered reliable enough to be used for Hf, as the common metal form is retrieved in soils.
The typical value kept for assessment: Kd of 2500 L/kg.
This coefficient confirmed a high adsorptivity of the substance on particulate matter and low mobility in soils, leading to a poor availability to biota in water.
Key value for chemical safety assessment
Additional information
Other adsorption coefficient indicated as dimensionless:
- log Kp (soil-water) ,3.4
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