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Environmental fate & pathways

Adsorption / desorption

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Description of key information

For the mixture no data on adsorption properties are available. Adipic acid is applied for read-across approach. The estimated Koc values for adipic acid, using different accepted calculation methods are 2.4, 5.3 and 21.5 (Currenta, 2009).

Key value for chemical safety assessment

Additional information

There is no adsorption / desorption test for dicarboxylic acids available.

Under environmental relevant pHs, adipic-, succinic- and glutaric acid exist predominantly in the dissociated form, based upon the individual pKa values of each cinstituent. At pH 5 to 9, the substances will be deprotonated resulting in the corresponding anion. As cationic substances in particular generally adsorb strongly, an adsorption potential of the dissociated form of the dicarboxylic acids is not expected. Nevertheless, in order to predict the mobility and fate of dicarboxylic acids in soil and sediments results from adipic acid were used, since the physico-chemical properties are very similar to the other dicarboxylic acids, and data on Koc for adipic acid are already estimated. For that purpose, the organic carbon-water partition coefficient (Koc) is calculated (Currenta, 2009) using different estimation methods following the recommendations of the Guidance document on information requirements and chemical safety assessment, chapter R.7a: Endpoint specific guidance document R.7a (ECHA, 2008). The log Kow of 0.093 was measured at pH 3.3, where the substance exists in its neutral from. This value is used as a worst-case assumption for calculation of the adsorption coefficient. Methods for estimating Koc, based on statistical relationships between Koc and the octanol/water partition coefficient (Kow) are used for calculation. Moreover, the Koc is estimated with the EPI Suite program (v. 3.20) of the U.S. Environmental Protection Agency. Here, calculations are based upon the molecule structure using the molecular connectivity method.