Registration Dossier

Diss Factsheets

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Diquat C16 -18 (N,N,N',N',N''-Pentamethyl-N-C16-18 (even numbered) C18 unsat.-alkyl-1,3-propanediammonium chloride) dissolves well in water and will have a very low vapour pressure. Despite of the relatively high water solubility the CMC at pH 7 of 790 mg/L was used as the water solubility value to be used in the prediction of partitioning processes as this is considered to be more realistic for surface active substances. 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 low as diquat will sorb strongly to sorbents both based on hydrophobic and ionic interaction where the ionic interaction will govern the partitioning process. Kd ranging from 16000 to 190000 L/kg were observed for loamy sand and clay soil indicating that the substance has a low leaching potential.

The Kdvalues observed is for both Speyer 6S clay soil and Eurosoil 4 silt soil, are outside the advised maximum range of 5 * 104L/kg (or Kocof 1 * 106L/kg) for sediment and soil and therefore this maximum value will be used as a realistic worst-case to derive the distribution constants for the diquat C16-18.

Because there is no principal difference between soil and sediments considering the sorption properties and because for cationic surfactants the degree of sorption is not related to the organic carbon content, the value for soil will also be used for sediment and suspended particles.

Categories Display