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EC number: 939-967-7
CAS number: -
- Soil B (the calcareous soil) had more affinity for Zr than soil A (the
acidic soil) and sorption also occurred faster in soil B. This may be
explained by the fact that the H+ ions present in the acidic soil enter
in competition with Zr ions for adsorption to available sites on the
- The very low soil:solution ratio used in this study was necessary
because at higher ratios the concentrations of Zr in solution would be
below the detection limit of the available method of analysis. However,
such low soil:solution ratios favor adsorption and therefore the Kp
values may have been affected by these experimental conditions.
- The method of Kp determination does not allow to distinguish between
the different solid forms of Zr in the experiment (adsorbed to iron
oxides, adsorbed to organic matter, precipitated as hydroxydes or
carbonates). According to formerly obtained results, the authors mention
that adsorption to iron oxides may be the predominant process in soil.
- The desorption experiments indicate that the concentrations of Zr in
soil remain largely unaffected, suggesting that non-reversible processes
are involved such as inner sphere complexation or surface precipitation.
Literature data were added to this dossier to provide more insight on the expected behaviour of the substance. First, erbium zirconium oxide is extremely insoluble in water, hence will only release minor amounts of free metal ion to the aquatic part of the environmental compartment under consideration. Therefore, adsorption is considered to be a less important process determining the fate and behaviour of the substance in the environment. Individual data on the adsorption capacity of zirconium is included in this dossier. A total of five studies was used in a weight of evidence approach to cover the endpoint. Reliable data were available for soil, suspended matter, and sediment. The following final key values were retained: a log Kp of 5.00 for suspended matter-water, a log Kp of 5.48 for sediment-water, and a log Kp of 4.13 for soil-water. Adsorption to sediment and suspended matter appears to be slightly more pronounced than for soil for zirconium. For erbium, data on adsorption capacity are not included in this dossier, but a similar moderate to strong adsorption capacity can be expected as for zirconium.
Information on zirconium
In total, five reliable studies were identified containing relevant information on adsorption of zirconium to particulate matter. These studies were used in a weight of evidence approach. Data were available for soil, sediment, and suspended matter and will be further discussed below.
For suspended matter, two studies were identified as useful. Veselý et al. (2001) reported a median log Kp of 3.23 for a series of samplings along Czech rivers. Gobeil et al. (2005) analysed samples from several locations along the St. Lawrence river, at one location river water was sampled and at the other location effluent of the Montreal waste water treatment plant was sampled. Based on average concentrations of zirconium in filtered water and suspended particulate matter, log Kp values of 6.26 and 5.51 were calculated for these locations. Because there is a limited amount of values available, the average log Kp of 5.00 for these two studies is selected as key value for characterising distribution between suspended matter and water.
For sediment, only one reliable study is available (Klimisch score of 2). In this study, zirconium concentrations were determined in paired samples of filtered water and sediment from 20 sites along the Blesbokspruit, South Africa. Based on data from this study (Roychoudhury and Starke, 2006) an average log Kp value of 5.47 L/kg was calculated, the range being 5.12-5.92.
For soil, two reliable studies were retained for the determination of the key value. Ferrand (2005) (see also Ferrand et al., 2006) conducted batch equilibrium experiments with ZrOCl2 solutions and two different soils (acidic sandy clayey loamy soil and a clayey calcareous soil). The Kp values resulting from this study were 6,000 L/kg (dw) (or log Kp of 3.78) for the acidic soil and 30,000 L/kg (dw) for the calcareous soil (or log Kp of 4.48). The median value of 4.13 was taken as key log Kp for soil.
Overall, strong adsorption of zirconium to particulate matter is observed, whether soil, sediment, or suspended matter.
Information on erbium
For erbium, data on adsorption capacity are not included in this dossier, but a similar moderate to strong adsorption capacity can be expected as for zirconium.
Conclusion on erbium zirconium oxide
Erbium zirconium oxide is extremely insoluble in water, hence will only release minor amounts of free metal ion to the aquatic part of the environmental compartment under consideration. Therefore, adsorption is considered to be a less important process determining the fate and behaviour of the substance in the environment. Individual data on the adsorption capacity of zirconium is given above. Zirconium has a moderate to strong adsorption capacity to particulate matter. A similar adsorption capacity can be expected for erbium.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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