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Environmental fate & pathways

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Hydrolysis

Zirconium basic carbonate is an inorganic substance, which is poorly water soluble. In the case of zirconium basic carbonate a release of free zirconium ions is to be expected in a relevant amount at pH < 4 (with bicarbonate or carbon dioxide as anion).

At pH values above 6, salt hydrolysis can also occur, forming zirconium bicarbonate and insoluble zirconium hydroxide with increasing pH. However, with respect to the poor water solubility of the test item, this process is negligible. The chemical equilibrium is clearly on the side of the insoluble zirconium carbonate.

Biodegradation

Due to its inorganic nature, biodegradation studies can be waived (REACH Annex VII, 9.2.1.1 column 2).

Bioaccumulation

Due to its extremely low water solubility, the substance will not reach high concentrations in the water, so bioaccumulation in aquatic organisms can be regarded as negligible. Furthermore, due to complexation to organic matter, zirconium basic carbonate will become unavailable both for aquatic and sediment-dwelling organisms. Based on experimental data available for algae and cyanobacteria (read across from zirconium dichloride oxide, a 'water soluble' zirconium compound), zirconium has no potential to bioconcentrate/bioaccumulate in the aquatic foodchain. Experimental data for terrestrial plants (experiments conducted with zirconium dichloride oxide, zirconium acetate, and zirconium hydroxide, i.e., two 'water soluble' and one 'insoluble' zirconium compound) confirm that neither for the terrestrial foodchain there is a concern for bioaccumulation.

Transport and distribution

Adsorption of zirconium compounds (as such) to particles of suspended matter, sediment, or soil, is not expected to occur. It is rather the zirconium cation (or potentially other cationic zirconium species) that will adsorb to particulate matter. Therefore, the assessment of the potential for adsorption and the derivation of adsorption coefficients is element-based (not substance-based). Based on the derived Kp values, zirconium can be concluded to strongly adsorb to particulate matter. Therefore, its environmental distribution will be mainly to sediment and soil, depending on the emission pathway under consideration. For adsorption to occur however, zirconium has to end up in the aqueous phase of the environmental compartment under consideration (water column, or pore water in sediment/soil).