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Environmental fate & pathways

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Read-across approach

In the assessment of the environmental fate and pathways of zinc dibenzoate, 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, zinc dibenzoate will completely dissociate and only be present in its dissociated form, i.e. as zinc cation and benzoate anion.

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. Predictions of stability of zinc dibenzoate in a standard ISO 6341 medium (2 mMCaCl2, 0.5 mM MgSO4, 0.77 mM NaHCO3 and 0.077 mM KCl, pH 6 and 8) clearly show that monodentate ligands such as benzoic acid have no potential for complexing zinc ions in solution (Visual minteq. Version 3.0, update of 18 October 2012. http://www2.lwr.kth.se/English/OurSoftware/vminteq/index.html).

Upon dissolution and dissociation of zinc dibenzoate into Zn2+ and the benzoate anion, 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 (Zn2+ and benzoate 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).