Biodisposition of linear alkylbenzene sulphonates and their associated sulphophenyl carboxilic acid metabolites in sea water

The present paper describes the results of the application of the biodegradation assay proposed by the United States Environmental Protection Agency “Biodegradability in sea water” Office of Prevention, Pesticides, and Toxic Substances 835.3160, in shaked flask, to linear alkylbenzene sulphonate (LAS), the synthetic surfactant with the highest consumption volume on a world-wide basis. The concentration of sulphophenyl carboxylic acids (SPCs) which are the main metabolites of LAS have also been monitored by high performance liquid chromatography. The experiment were conducted using water originating from the Bay of Cádiz (in the South West of the Iberian peninsula). The results indicate that LAS was rapidly biodegraded. SPCs were transiently produced during the process and they were biodegraded to levels below the limits of detection (136 μg/l) after 42 days of assay. The kinetic of biodegradation of the surfactant and its biointermediates have been modeled; half-life times of 6.2 days for the primary biodegradation of LAS and of 9.6 days for the mineralization of the biointermediates were obtained.