Reaction mass of Benzene sulfonic acid, hexadecyl(sulfophenoxy)-,disodium salt and Benzene sulfonic acid, - oxibis[hexadecyl]-, disodium salt

Biodegradation in water and sediment: simulation tests

Description of key information

Biodegradation of Dowfax 8390 was observed in soil and sediment studies using 14C radiolabelled test substance.

Key value for chemical safety assessment

Half-life in freshwater:

2.2 d

at the temperature of:

21 °C

Half-life in freshwater sediment:

2.2 d

at the temperature of:

21 °C

Additional information

In a river sediment study, under aerobic conditions, 89% of the [14C]MADS (a major component of Dowfax 8390) was degraded to [14C]products within 7 days. Mineralization of [14C]MADS to 14CO2 reached 5% after 83 days, and 15% after 181 days. Mineralization of [14C]MADS to 14CO2 reached approximately 2% after 181 days in reaction mixtures initially incubated under aerobic conditions for 7 days, followed by anaerobic incubation. Little degradation of [14C]MADS was detected in reaction mixtures incubated under exclusively anaerobic conditions.

In a separate soil and sediment study, within one year, mineralization of [14C]MADS to 14CO2 was observed in all of the soil and sediment mixtures, with an average of 51 ± 19% of the radioactivity added (± 1 standard deviation). Mineralization of [14C]MADS in biologically-inhibited controls, prepared with 2% formalin, was </= 0.3%, confirming that the mineralization observed in the viable mixtures was biologically mediated. Since these soils and sediments came from diverse environments, these results indicate that microorganisms capable of completely degrading DOWFAX 8390 Surfactant appear to be ubiquitous. Mineralization of [14C]MADS reached 3 to 8% after 3 weeks. This level of mineralization was consistent with results from previous biodegradation studies using fresh, un-acclimated activated sludge.