Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Stability:

In contact with water or the moisture of air, Zirconium tetrachloride decomposes instantaneously according to the following equation:

ZrCl4+ H2O -> ZrOCl2+ 2 HCl

Then, ZrOCl2 under environmental conditions will hydrolyse generating HCl and precipitating into ZrO2 according to the equation:

ZrOCl2+ H2O -> ZrO2+ 2 HCl

Therefore, the final degradation product of ZrCl4is ZrO2, which has very low water solubility (0.055 mg/L) and which is thus stable in water. The chemical behaviour ZrO2in water is highly dependent on the water chemistry and the hydroxide species presents in solution that could lead to complex formation.

In terms of environmental toxicity, the relevant degradation product to characterize the effect of ZrCl4to aquatic, benthic and terrestrial organisms is therefore ZrO2(or indirectly ZrOCl2). Thus, most of the studies reported in this dossier are used for a read-across approach from Zirconium compounds leading to the formation of ZrO2.

Biodegradation:

Zirconium tetrachloride is inorganic and can therefore not undergo any microbial degradation in the environment.

Bioaccumulation:

Considering the most stable form of Zirconium tetrachloride in the environment (ZrO2), bioaccumulation is not expected due to the low water solubility of ZrO2(0.055 mg/L). Therefore, the substance will not reach high concentrations in water and will not be bioavailable to organisms, so bioaccumulation can be regarded as negligible. 

Adsorption/Desorption:

Relating to the Kd values, Zirconium compounds display strong affinity for the solid phase of the soil particle (mean Koc value of 41044).