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EC number: 231-176-9
CAS number: 7440-67-7
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.
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
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