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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Adsorption to the solid soil phase is not expected.

Key value for chemical safety assessment

Additional information

Since no studies on the adsorption potential of (2-hydroxyethyl)ammonium nitrate are available, the assessment has been performed with the substance’s dissociation products.

For 2-aminoethanol a logKoc of 0.067 has been calculated based on estimates from MCI [BASF SE, SRC KOCWIN v2.00, 2010].

The molecule is not expected to adsorb to suspended solids and sediment based upon the logKoc as calculated for the uncharged molecule. However, a pKa value of 9.5 indicates that the molecule will exist primarily as a cation in the environment and cations generally adsorb stronger to soils containing organic carbon and clay than their neutral counterparts. Hence, the PCKOC-model may underestimate adsorption to organic carbon since it does not consider the ionic structure of the molecule. Under environmental conditions (pH from 5 to 9) 2 -aminoethanol is almost completely present in its charged form (as calculated by the formula: % ionised = 100/(1+10(pKa - pH)): 97% at a pH of 8, 100% at lower pH values).

To consider the pH-dependent molecule speciation, the calculated logKoc was therefore pH-corrected by a calculation method developed by Franco & Trapp (2008) which resulted in a logKoc of 1.16 for pH 7.

Concerning the adsorption potential of sodium nitrate, it can be stated that simple inorganic salts with high aqueous solubility will exist in a dissociated form in an aqueous solution. Such a substance has a low potential for adsorption. In addition a screening study (OECD 121) could not be conducted as it is technically not feasible to perform and QSARs are not suitable for such substances.

Conclusively, adsorption of (2 -hydroxyethyl)ammonium nitrate to the solid soil phase is not expected.