Fatty acids, C8-10, zinc salts

Endpoint summary

Description of key information

FATTY ACIDS, C8 -10, ZINC SALTS:

Based on the solubility of fatty acids, C8-10, zinc salts in water, its environmental fate and pathways are defined by the mobility of zinc cations and fatty acid (C8-10) anions under environmental conditions. Thus, transport and distribution of substance Fatty acids, C8-10, zinc salts in the environment is most accurately evaluated by separately assessing the fate of its moieties zinc and fatty acids, C8-10. Please refer to the information given in the respective assessment entities. In brief:

 

FATTY ACIDS, C8-10:

QSAR estimates indicate an affinity of fatty acids to solid phases. Koc values of 69.63 L/kg for octanoic acid and 261.8 L/kg for decanoic acid were estimated based on QSAR using EPISuite (V.4.00 - 4 .11) from a logKow of 3.05 and 4.09, respectively. However, fatty acids are readily biodegradable by sludge microorganisms and also by soil/sediment microorganisms and are thus expected to get readily biodegraded while adsorbed. Therefore, accumulation in the environment is unlikely.

 

ZINC:

For metals, the transport and distribution over the different environmental compartments e.g. the water (dissolved fraction, fraction bound to suspended matter), soil (fraction bound or complexed to the soil particles, fraction in the soil pore water,...) is described and quantified by the metal partition coefficients between these different fractions. Information on these partition coefficients is given under 5.6. Partition coefficients for zinc in freshwater have been reviewed in the RAR (ECB 2008). Based on this experimental evidence, a partition coefficient for the distribution between solid particulate matter and water (Kpsusp) of 5.04 (log value) has been defined for EU waters and was used throughout the RAR..

The Kp for the distribution between sediment and water (Kpsed) was estimated in the RAR from that for particulate matter, as follows: Kpsed= Kpsusp/ 1.5, based on the average difference in concentrations of zinc and other metals in both media. For zinc this results in a Kpsedof 73,000 l/kg. (ECB 2008) These partition coefficients have been used since then in other legislative processes in the EU (e.g. the water framework directive) and will also be used for REACH. For the marine water, a partition coefficient water/suspended matter of 6010 l/kg has been derived.

For soil, a solids-water partitioning coefficient of 158.5 l/kg (log value 2.2) was determined experimentally on 11 American soils. This value was used in the RA Zinc.