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Environmental fate & pathways

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Environmental distribution of a substance  is mainly driven by the adsorption potential. The potential of aluminium for adsorption to sediment and soil particles is mainly driven by its speciation and the concentration of dissolved organic carbon (DOC).

Aluminium speciation is very complex and changes significantly with the pH. In the absence of organic matter, Al3+is the predominant aluminium species at low pH (less than 5.5).  As pH increases above 5.5, aluminium-hydroxide complexes formed by hydrolysis become increasingly important and dominate aqueous aluminium speciation. The presence of a moderate amount of organic matter in soft water results in organically complexed aluminium being the dominant aluminium form when the pH is between 4 and 7.  Above pH 7, anionic aluminium hydroxide predominates. 

The DOC and the pH are also affecting the adsorption and desorption of aluminium to organic particles. For evaluation of adsorption at different pH-levels a chemical simulation was performed. As a result it can be concluded that the potential for adsorption is low at different pH-levels. Approximately 8% of the total aluminium were bound to particles with was further reduced to < 1% at pH-values > 7 (at soft and hard water). Log Kd-values of 3 - 5 were derived.