Barium 4-dodecylphenolate

Endpoint summary

Description of key information

The fate of barium 4-dodecylphenolate in the environment is most accurately evaluated by separately assessing the fate of its moieties barium and 4-dodecylphenolate. Since barium cations and 4-dodecylphenolate anions behave differently in the environment, including processes such as stability, degradation, transport and distribution, a separate assessment of the environmental fate of each assessment entity is performed. Please refer to the data as submitted for each individual assessment entity.

 

Barium: Hydrolysis, phototransformation, and biodegradation are not relevant for inorganic substances like barium. Barium is not considered to be (bio)degradable. Bioconcentration and bioaccumulation are not considered to be relevant for inorganic barium substances and elemental barium. The coefficient for partitioning of barium between particulate matter and water (Kpsusp) of 5,217 L/Kg was derived for EU waters whereas the Kp for the distribution between sediment and water (Kpsed) was estimated with 3,478 L/kg. For soil, a solids-water partitioning coefficient of 60.3 L/kg was determined experimentally.

4-dodecylphenolate is not readily biodegradable and does not contain hydrolysable groups. Thus, abiotic and biotic degradation is not expected to affect the fate in the environment. Further, according to the QSAR-based predictions (Molecular Connectivity Index model of KOCWIN v2.00), the log Koc is 4.695, corresponding to a Koc of 49540 L/kg.

 

Additional information

Read-across

 

Barium 4-dodecylphenolate consists of a metal cation and a phenolate anion. Based on the solubility of barium4-dodecylphenolate in water, dissociation of barium 4-dodecylphenolate resulting in barium cations and 4-dodecylphenolate 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 barium 4-dodecylphenolate could not be identified. Data for barium appear to be generally limited. However, barium ions tend to form complexes with ionic character as a result of their low electronegativity. Further, the ionic bonding of barium is typically described as resulting from electrostatic attractive forces between opposite charges, which increase with decreasing separation distance between ions.

 

Based on an analysis by Carbonaro et al. (2011) of monodentate binding of barium to negatively-charged oxygen donor atoms, monodentate ligands such as 4-dodecylphenolate anions are not expected to bind strongly with barium.The analysis by Carbonaro & Di Toro (2007) suggests that the following equation models monodentate binding to negatively-charged oxygen donor atoms of functional groups:

log KML= αO* log KHL+ βO; where

KML is the metal-ligand formation constant, KHL is the corresponding proton–ligand formation constant, and αO and βO are termed the Irving–Rossotti slope and intercept, respectively. Applying the equation and parameters derived by Carbonaro & Di Toro (2007) and the pKa of dodecylphenol of 10.31 results in:

log KML= 0.186 * 10.31 – 0.171

log KML= 1.75 (estimated barium 4-dodecylphenolate formation constant).

Thus, it may reasonably be assumed that based on the estimated barium-dodecylphenolate formation constant, the respective behaviour of the dissociated barium cations and 4-dodecylphenolate anions in the environment determine the fate of barium 4-dodecylphenolate 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.

In the assessment of environmental fate and pathways of barium 4-dodecylphenolate, read-across to the assessment entities soluble barium substances and 4-dodecylphenolate is applied since the ions of barium 4-dodecylphenolate determine its environmental fate. Since barium cations and 4-dodecylphenolate anions behave differently in the environment, including processes such as stability, degradation, transport and distribution, a separate assessment of the environmental fate 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 barium 4-dodecylphenolate.