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Environmental fate & pathways

Adsorption / desorption

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Description of key information

The measured log Koc values for an analogous and more hydrophobic surfactant substance ranged from 4.54 to 4.81. The DOWFAX 2A1 substance differs from this reference substance in that the alkyl chain (hydrophobe) has four fewer methylene carbons, and thus will have a lower expected Koc value. A value of log Koc = 3.0 is used in the chemical safety assessment, as this provides a more conservative basis (resulting in lower PNECsoil and PNECsed values via the equilibrium partitioning method. The substance can be regarded as having moderate potential for adsorption to organic matter of soil, sediment, and wastewater biosolids.

Key value for chemical safety assessment

Koc at 20 °C:
1 000

Additional information

The adsorption/desorption of a structurally similar surfactant (DOWFAX 8390) was evaluated on three soils, according to OECD guideline 106. The DOWFAX 8390 substance may be regarded as more hydrophobic and having higher adsorption potential than DOWFAX 2A1, as the former substance has mono- and di-alkyl C16 groups while the latter has C12 groups. Based on results for DOWFAX 8390, the experimentallog Koc values for this substance ranged from 4.54 to 4.81.   Linear regression of measured log Koc values for a series of C6, 8,10, and 12 normal alcohols gives a linear relationship, with contribution of each methylene carbon of log Koc = 0.43. Since DOWFAX 2A1 has four fewer methylene groups (i.e, correction to log Koc = 4 * 0.43 = 1.7) than DOWFAX 8390, log Koc of approximately 2.8 to 3.1 can be derived for DOWFAX 2A1. Based on a midpoint estimate of log Koc = 3.0, the DOWFAX 2A1 substance can be regarded as having moderate potential for adsorption to organic matter of soils, sediments, and wastewater biosolids.

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