Registration Dossier

Environmental fate & pathways

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ISSUES IN ADSORPTION AND DISORPTION MEASUREMENTS OF CATIONIC SURFACTANTS

The registration substance is a cationic surfactant with strongly basic nitrogen atoms. It is well known from cationic surfactants like protonated primary, secondary, tertiary and quaternary amines that sorption to solids is not only via van der Waals forces but also by ionic interactions like ion pair formation and ion exchange. The Koc for cationic surfactants cannot be measured with the HPLC Method (OECD 121) nor estimated reliably. Measuring with 14C material in an OECD106 Batch test is the only reliable and feasible method. Unfortunately it is not feasible to synthesize a representative 14C registration substance and therefore an OECD 106 test cannot be performed. Instead read-across is an available option.

ADSORPTION / DESORPTION

READ-ACROSS OPTION TO 14C C22 alkyl trimethyl ammonium chloride

The ionic interactions usually are dominating for cationic surfactants and therefore it is justified to use the measured Kd values of soil, sediment and sludge from the cationic 14C-C22 alky trimethyl ammoniumchloride (14C-C22 ATQ) and used it as a worst case.

In the table below the measured Kd values for 14C-C22 ATQ is given as well as the translated values for the Exposure modelling program EUSES 2.1

 

OECD106 results

at 10 µg/L 14C-C22 ATQ

EUSES STANDARD VALUES %OC

and Kd related to Koc

SOIL

 

 

 

 

 

 

% OC

Koc (L/kg) average
lowest conc.
Measured

% OC
EUSES

Kd (L/kg) EUSES
based on EUSES OC

EUSES Term for
Compartment

Cranfield 164

3.7

52486

 

 

 

Cranfield 277

2.7

543315

 

 

 

Cranfield 299

2.9

309138

 

 

 

mean

3.1

226807

2

4536

SOIL

 

 

 

 

 

 

SEDIMENT

 

 

 

 

 

SW

11.1

29258

5

1463

SEDIMENT

 

 

 

 

 

 

SLUDGE

 

 

 

 

 

secondary (activated)

39.9

731

37

270

ACTIV. SLUDGE