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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Depending on the pH of the medium, the ratio between the 2 forms of the registered substance (carboxylic acid/carboxylate) may vary. Due to the presence of an ionised form, only the method developed by Bintein and Devillers (1994) is fully applicable. The calculated Koc is around 0.9 and the corresponding LogKoc is -0.05.

However it should be noted that the substance is considered as readily biodegradable which is a condition of exemption to further evaluate the Koc of the registered substance.

Key value for chemical safety assessment

Koc at 20 °C:
0.9

Additional information

In the table here-below are gathered all the calculated values of LogKoc, depending on the applied method and the targeted structure:

 Target Method  Calculated value (LogKoc) Mean Log Koc
 Acid+Salt Bintein and Devillers (1994)  LogKoc(soil)=-0.069, LogKoc(sediment)=-0.033  -0.051
 Acid Sabljic and Güsten (1995) LogKoc(alcohol, organic acid)=1.83, LogKoc(organic acid)=2.01  1.92
 Acid  KOCWIN (EPISUITE) LogKoc(MCI)=1.383, LogKoc(Kow)=1.306  1.345
 Salt  KOCWIN (EPISUITE) LogKoc(Kow)=-0.855 -0.855 

It appears that the non ionised structure (acid) has a non negligeable LogKoc value (from 1.3 to 1.9), in line with the high LogKow value (around 2.3 -see section 4.7). The carboxylate form (salt) is characterised by a low LogKoc value (-0.855) which is relevant regarding the chemical structure, even if the calculation is of poor reliability (Klimisch code 3). Finally, the model considering the behaviour of the neutral form (acid) and the ionised form (salt) at environmental pH (Bintein et Devillers, 1994) reflects the expect values regarding the intrinsic properties of the two chemical forms.

The results obtained with these methods give a good picture of the behaviour of the registered substance between the water and the organic matter. These results, their quality and the relevance have to be evaluated in conjunction with two aspects:

- the calculations show a low potential of the registered substance to adsorbe onto the organic matter,

- the registered substance is considered as readily biodegradable.

Therefore the LogKoc is unlikely to strongly influence the behaviour of the registered substance in the environment, and further testing on this endpoint may not be justified.

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