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Environmental fate & pathways

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The fate of zinc 5-nitroisophthalate in the environment is most accurately evaluated by separately assessing the fate of its constituents zinc and 5-nitroisophthalate.

 

In transformation/dissolution tests according to the OECD Series on Testing and Assessment Number 29 (2001) with a loading of 1 mg/L, a nearly complete dissolution was already observed after 24 h resulting in dissolved Zn concentrations of 247 microg Zn/L at pH 6 and 213 a microg Zn/L at pH 8 (corresponding to 991 and 853 microg/L zinc 5-nitroisophthalate, respectively). Thus, zinc 5-nitroisophthalate is soluble and expected to dissociate upon contact with water and to release zinc cations and nitroisophthalate anions. The respective dissociation is reversible and the ratio of the salt /dissociated ions is dependent on the metal-ligand dissociation constant of the salt, the composition of the solution and its pH.

 

In the assessment of enviromental fate of zinc 5-nitroisophthalate, read-across to the assessment entities soluble zinc substances and 5-nitroisophthalic acid is applied since the ions of zinc 5-nitroisophthalate determine its environmental fate. Since zinc cations and nitroisophthalate anions behave differently in the environment, including processes such as stability, degradation, transport and distribution, a separate assessment of the environmental fate of each assessment entity is performed. Please refer to the data as submitted for each individual assessment entity.

 

Zinc: Hydrolysis and biodegradation are not relevant for zinc. Zinc is an essential element that is actively regulated by organisms. Bioconcentration and bioaccumulation are not considered to be relevant for inorganic zinc substances. The coefficient for partitioning of zinc between particulate matter and water (Kpsusp) of 109,648 L/Kg was derived for EU waters whereas the Kp for the distribution between sediment and water (Kpsed) was estimated with 73,000 L/kg. For saltwater, a partition coefficient water/suspended matter of 6010 L/kg was derived. For soil, a solids-water partitioning coefficient of 158.5 L/kg was determined experimentally.

 

5-nitroisophthalic acid: Regarding abiotic degradation, 5-nitroisophthalic acid does not contain any components that can hydrolyse in water at an environmentally relevant pH. Further, according to the QSAR-based predictions, 5-nitroisophthalic acid may not be considered as ready biodegradable and the logKoc of 5-nitroisophthalic acid is 2.09 (Koc = 123.1 L/kg).

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