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Environmental fate & pathways

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Zirconium, acetate lactate oxo ammonium complexes consists of ammonium [NH4]+ and zirconium [Zr]4+ cations and acetate [CH3COO]2- and lactate [CH3CH(OH)COO]2- anions. A complete dissociation of zirconium, acetate lactate oxo ammonium complexes resulting in ammonium, zirconium, acetate and lactate ions may be assumed under environmental conditions. Since acetate, ammonium, lactate and zirconium ions upon release behave differently in the environment, the fate of acetate, ammonium, lactate and zirconium ions in the environment is assessed separately.

 

Acetate in the form of sodium acetate is used as reference substance in the OECD 301 test on "Ready Biodegradability" (1992) where it reliably meets the criteria of ready biodegradability (i.e. 70% removal of DOC and 60% of within a 10-d window) even when an inoculum is not deliberately added. Further studies on biodegration confirm that acetate is readily biodegradable.

 

Lactate as common fermentation product and substrate for anaerobic microorganisms is rapidly biodegraded.

 

Available evidence points to a ready biodegradability of ammonium under aerobic conditions (i.e. source of bioavailable nitrogen). Ammonium is not persistent in water and rapidly degraded by two-step-oxidation to nitrate, a process called “Ammonia oxidation”, which represents one of the endpoints investigated in OECD 209 activated sludge respiration inhibition test.

The concept of biodegradation is not applicable to inorganic substances. Zirconium is an inorganic element and thus biodegradation is not relevant.

In sum, biotic degradation is expected for acetate, ammonium and lactate ions but not for zirconium.

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