Reactivity and fate of secondary alkane sulfonates (SAS) in marine sediments

- Anionic surfactant SAS can be anaerobically degraded in marine sediments.
- Degradation is strongly influenced by the sorption capacity of SAS homologues.
- Oxidation of SAS alkyl chain takes place by means of fumarate addition.
- Carboxylic acids are formed during the anaerobic degradation of SAS.

This research is focused on secondary alkane sulfonates (SAS), anionic surfactants widely used in household applications that access aquatic environments mainly via sewage discharges. We studied their sorption capacity and anaerobic degradation in marine sediments, providing the first data available on this topic. SAS partition coefficients increased towards those homologues having longer alkyl chains (from up to 141 L kg−1 for C14 to up to 1753 L kg−1 for C17), which were those less susceptible to undergo biodegradation. Overall, SAS removal percentages reached up to 98% after 166 days of incubation using anoxic sediments. The degradation pathway consisted on the formation of sulfocarboxylic acids after an initial fumarate attack of the alkyl chain and successive β-oxidations. This is the first study showing that SAS can be degraded in absence of oxygen, so this new information should be taken into account for future environmental risk assessments on these chemicals.