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Environmental fate & pathways

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Read-across approach

In the assessment of the environmental fate and pathways of zirconium propionate (CAS: 84057-80-7), a read-across approach from data for the metal cation and the organic anion is followed. This read-across strategy is based upon the assumption that upon release to the environment and dissolution in aqueous media, zirconium propionate will completely dissociate and only be present in their dissociated form, i.e. as zirconium and propionate ions.

Upon dissolution in water, it is indeed predicted that metal carboxylates dissociate completely into the metal cation and the organic anion at environmentally relevant conditions. Information on the stability constant of zirconium propionate predicts that in a standard ISO 6341 medium (2 mM CaCl2, 0.5 mM MgSO4, 0.77 mM NaHCO3and 0.077 mM KCl, pH 6 and 8) propionic acid has no potential for complexing zirconium ions in solution (<1% of total metal concentration complexed at 0.001 mM Zr; Visual minteq. Version 3.0, update of 18 October 2012. http://www2.lwr.kth.se/English/OurSoftware/vminteq/index.html). It is further predicted that upon dissociation in water, the liberated zirconium ion will immediately precipitate as ZrO2or Zr(OH)4, resulting in extremely low dissolved zirconium concentrations.

Upon dissolution and dissociation of zirconium propionate into zirconium and propionate ions, both constituent ions will each show its proper (bio)degradation, bioaccumulation and partitioning behaviour in the environment, as reported for the corresponding metal ion and carboxylic acid (zirconium and propionic acid). The environmental fate and behaviour for the metal and organic moieties is predicted to be clearly different from each other, resulting in a different relative distribution over the environmental compartments (water, air, sediment and soil).