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Environmental fate & pathways

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The fate of fatty acids, C9 -13 neo, potassium salts in the environment is most accurately evaluated by separately assessing the fate of its moieties potassium and fatty acids, C9 -13 neo or rather its structural analogue neodecanoic acid. In the assessment of environmental fate and behaviour of fatty acids, C9 -13 neo, potassium salts, data available for the potassium cation and the neodecanoate anion indicate that abiotic and biotic degradation in respective compartments do not contribute significantly to its fate in the environment.

Potassium:

Biotic degradation is not relevant for metals and metal compounds. Potassium as an element is not considered to be (bio)degradable.

Transport and distribution:Dissolved potassium occurs in solution as dissociated K+ ions. Although K is an abundant element, its mobility in soils, sediments and suspended matteris limited since it is readily incorporated into clay lattices and it is adsorbed more strongly than Na+ to the surfaces of clay minerals and organic matter (Salminen, 2005).A European median log Kp value of 3.99 L/kg is derived for sediment-water partitioning.

Neodecanoic acid:

Abiotic degradation is not considered to significantly affect the environmental fate of neodecanoic acid since neodecanoic acid is lacking hydrolysable functional groups and does not absorb light within a range of 290 to 750 nm.

Biotic degradation: Neodecanoic acid is not readily biodegradable (11% biodegradation in 28 d) based on results from a standard OECD ready biodegradation test. Studies are not available to assess the biodegradability of neodecanoic acid under simulated conditions or in soil, but given the limited biodegradation in water, biodegradation under simulated conditions, or in soil is not expected to occur to a great extent.

Transport and distribution: The estimated Koc of neodecanoic acid is 121 and may be sensitive to pH. The vapor pressure is very low, i.e. 0.65 Pa suggesting a limited volatilization from soil. Henry’s Law constant for neo-decanoic acid is calculated with 0.54 Pa-m3/mole at 25 °C indicating that volatilization from water is not expected to occur at a rapid rate, but may occur. Neodecanoic acid is a weak organic acid with an estimated dissociation constant (pKa) of 4.69. Consequently, neodecanoic acid, at neutral pH, typical of most natural surface waters, is expected to dissociate to the ionised form and therefore to remain largely in water.

Additional information

Read across

 

Metal carboxylates are substances consisting of a metal cation and a carboxylic acid anion. Based on the solubility of fatty acids, C9 -13 neo, potassium salts in water, a complete dissociation resulting in potassium cations and neodecanoate anions may be assumed under environmental conditions. The respective dissociation is reversible, and the ratio of the salt /dissociated ions is dependent on the metal-ligand dissociation constant of the salt, the composition of the solution and its pH. A metal-ligand complexation constant of fatty acids, C9 -13 neo, potassium salts could not be identified. Data for alkaline earth metals appear to be generally limited. However, alkaline earth metals tend to form complexes with ionic character as a result of their low electronegativity. Further, the ionic bonding of alkaline earth metals is typically described as resulting from electrostatic attractive forces between opposite charges, which increase with decreasing separation distance between ions.Thus, it may reasonably be assumed that the behaviour of the dissociated potassium cations and neodecanoate anions in the environment determine the fate of fatty acids, C9 -13 neo, potassium salts upon dissolution with regard to (bio)degradation, bioaccumulation, partitioning resulting in a different relative distribution in environmental compartments (water, air, sediment and soil) and subsequently its ecotoxicological potential. Thus, in the assessment of environmental fate and pathways of fatty acids, C9 -13 neo, potassium salts, read-across to the assessment entities neodecanoate and soluble potassium substances is applied since the individual ions of fatty acids, C9 -13 neo, potassium salts determine its environmental fate. Since potassium ions and neodecanoate ions behave differently in the environment, regarding their fate and toxicity, a separate assessment of each assessment entity is performed. Please refer to the data as submitted for each individual assessment entity. For a documentation and justification of that approach, please refer to the separate document attached to section 13, namely Read Across Assessment Report for fatty acids, C9 -13 neo, potassium salts.