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Environmental fate & pathways

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Hydrolysis

As soon as zirconium sulfate will come into contact with water it will dissolve and hydrolyse under the release of sulfuric acid. Under natural conditions however a significant buffering capacity will exist and hence the hydrogen released will be absorbed; a decrease in pH is therefore not expected. The hydrolysis of zirconium sulfate will thus continue and this immediate hydrolysis will form zirconium dioxide which has an extremely low water solubility and will precipitate out of the solution.

Biodegradation

Zirconium sulfate as well as its final hydrolysis product zirconium dioxide are inorganic compounds and therefore not subject to biodegradation.

Bioaccumulation

Under environmental conditions it is expected that instantaneous hydrolysis of zirconium sulfate will occur with the formation of zirconium dioxide or other insoluble zirconium complexes. Therefore, the substance will not reach high concentrations in the aquatic environment, hence bioavailability to and bioaccumulation in aquatic organisms can be regarded as negligible. Furthermore, due to adsorption to organic and inorganic particulate matter, zirconium will become unavailable for sediment-dwelling organisms too. Based on experimental data available for algae and cyanobacteria (read across from zirconium dichloride oxide, another '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).