FATE OF LINEAR ALKYLBENZENE SULFONATE IN THE MISSISSIPPI-RIVER

The 2 800-km reach of the Mississippi River between Minneapolis, MN, a nd New Orleans, LA, was examined for the occurrence and fate of linear alkylbenzene sulfonate (LAS), a common anionic surfactant found in mu nicipal sewage effluents. River water and bottom sediment were sampled in the summer and fall of 1991 and in the spring of 1992. LAS was ana lyzed using solid-phase extraction/derivatization/ gas chromatography/ mass spectrometry. LAS was present on all bottom sediments at concentr ations ranging from 0.01 to 20 mg/kg and was identified in 21% of the water samples at concentrations ranging from 0.1 to 28.2 mu g/L. The r esults indicate that LAS is a ubiquitous contaminant on Mississippi Ri ver bottom sediments and that dissolved LAS is present mainly downstre am from the sewage outfalls of major cities. The removal of the higher LAS homologs and external isomers indicates that sorption and biodegr adation are the principal processes affecting dissolved LAS. Sorbed LA S appears to degrade slowly.