Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

The adsorption of Yb(III) on silica and aluminium is strongly dependent on pH. While adsorption at acidic pH values in negligible, Kd values at the pH range of ca. 6.6 to 8 range between 2,300 and 12,000. As Yb is highly insoluble (see section 4.8 of the present dossier) no study on hydrolysis was conducted. Due to its poor solubility it is not expected to be found in the water phase.

Additional information

Adsorption/Desorption conclusions are based on read-across from Yb(III). Due to the low water solubility of the metal components contained in the test substance (zirconium dioxide, ytterbium (III) oxide and hafnium dioxide), a full transformation/dissolution protocol was carried out to study the potential release of these metals to the environment.

After 7 and 28 days (nominal loading of 100 mg/L, pH 8), only ytterbium(III) was found in solution with a maximum concentration of 0.069 µg/L. Zirconium and hafnium were both below the detection limit of 0.07 and 0.02 µg/L, respectively. Therefore, information on ytterbium(III) is relevant for the assessment of environmental fate properties of ytterbium stabilized zirconium and hafnium oxide and adsorption studies with ytterbium are used in a read-across approach to fulfill the REACH requirements for endpoint 9.3.1 “Adsorption/desorption screening”.