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Environmental fate & pathways

Endpoint summary

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Alkyl amidoamine/imidazolines are mainly protonated under environmental conditions. This means that the protonated fraction will behave as salt in water and will have a very low vapour pressure. A vapour pressure of 0.000079 and 0.000039 mPa were measured for respectivily the DETA and PEPA based imidazoline at 20 °C. The solubility of this cationic surface active substance will be influenced by the pH and is difficult to determine because of the surface active properties. As an alternative as suggested by the REACH guidance R.7 the CMC at pH 7 and 23°C was determined.

The solubility in the form of CMC was measured for three types of Imidazolines, i.e. the DETA, TEPA and PEPA based imidazolines.

Evaporation from water is based on the low vapour pressure and the observed CMC values very unlikely. The actual dissolved concentration in water will be extremely low as alkyl amidoamines/imidazolines will sorb strongly to sorbents both based on hydrophobicity and ionic interaction where the ionic interaction will govern the partitioning process. Two refined sorption/desorption tests were performed for the resp. DETA and PEPA based imidazoline and for both identical sorption was observed. For silt soil a Kd of 47249 L/kg was observed indicating that once sorbed the substance has a low leaching potential.

The partitioning of cationic surfactants to soil/sediment should not be normalized to the organic carbon content as this normalisation assumes partitioning to the organic carbon fraction alone. The mean Kd can directly be used to calculate the soil and sediment-water partition coefficient and its use prevents the erroneous influence of the organic matter fraction on the exposure assessment.

Kdsoil= 47249 L/kg ==> Ksoil-water= 70874 m3/m3

For sediment the same mean Kd value should be used. For risk assessment there is except for the organic matter fraction in soil/sediment no intrinsic difference between soil and sediment and because there is no OC normalisation applied the same mean Kd should be used. This is not a new insight. This approach was approved by TC NES II 2006 for the EU risk assessment of the cationic primary alkyl amines.

Kdsed = 47249 L/kg ==> Ksed-water = 23624.7 m3/m3; Kdsusp sed = 47249 L/kg ==> Ksed-water = 11812 m3/m3

Because it is known that suspended matter contains more small particles an additional safety factor of 2 is applied for precautionary reasons to the equilibrium partitioning coefficient for suspended sediment: Kdsusp sed = 94498 L/kg ==> 23624.7 m3/m3.