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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

BCF values calculated from Zr uptake by microalgae and cyanobacteria display no accumulation in these organisms. Values range between 0.1-0.64 L/kg. The key value selected is for Chlorella emersonii with a BCF value of 0.64 L/kg. Indeed, due to its low  water solubility and the particular properties of zirconium to sorb on particles, the substance will not reach high concentrations in water, so bioaccumulation in aquatic organisms can be regarded as negligible. No further bioaccumulation test will be proposed. 

Key value for chemical safety assessment

BCF (aquatic species):
0.64 L/kg ww

Additional information

A study from Garnham et al. (1993) has considered the bioaccumulation of zirconium to microalgae and cyanobacteries.

Accumulation of zirconium metal, by the microalgal and cyanobacterial species examined was due to a single phase metabolism-independent "biosorption" because values of Zr accumulation after 5 min or 4 hours were equivalents. Metal-ion binding to algal cell walls occurs partly through an ion-exchange mechanism, with binding sites arising from amino- and carboxyl- groups as well as sulphates and imidiazoles associated with polysaccharides and proteins in the cell wall. Biosorption is therefore highly dependent on cell wall structure and differences in amounts of Zr bound between the microalgal species is probably due to differences in the cell walls. According the authors of the studies presented in the present dossier, the biosorption of Zr was dependent on competing cations. Differences between organims may be attributed to (1) differences in cell wall structure, (2) different amounts of extracellular polysaccharide and (3) the result expressed in dry weight which does not take into account differences in the surface area available for Zr binding. Overall, BCF values showed little to nor bioaccumalation in microalage and are ranged between 0.1 - 0.6 L/kg.

Another publication of E. Ferrand studied the transfer of Zr from 2 type of soils (acidic and calcareous) to tomato and pea plants during 7 -days exposure. The 2 soils were amended with 3 forms of zirconium : ZrOCl2 and Zr acetate and Zr(OH)4. Zr accumulated mainly in the roots, with Zr adsoption to the root surface being of minor relevance. Translocation to aerial parts was limited. In that context, BSAF values for root were the highest for Zr acetate and the lowest for Zr(OH)4. They were all <= 0.1 BSAF values for aeria parts.