Removal of linear alkylbenzenesulfonates (LAS) in the Tamagawa Estuary

Abstract

To examine the processes for removal of organic micropollutants in an estuary, the anionic surfactants linear alkylbenzenesulfonates (LAS) were measured in the Tamagawa Estuary (Japan). Six surveys were conducted along axial transects from zero salinity to the river-mouth. The distributions of LAS in dissolved and suspended phases in the estuarine water were determined by high-performance liquid chromatography (HPLC). Mixing diagrams demonstrated that LAS are removed from the estuarine water throughout the salinity range (0.1–29ℵ.). In summer, LAS were completely removed, but in winter, 80% of LAS input from freshwater was removed in the estuary and the remaining 20% was discharged to Tokyo Bay. It is estimated that a few hundred kilograms of LAS per day are removed in the estuary. The isomeric compositions of LAS suggest that LAS were biodegraded in the estuary. LAS concentrations in the estuarine sediments also show a seaward decrease. Laboratory incubation experiments and mixing experiments as well as the above surveys indicate that LAS removal in the estuary is mainly caused by microbial degradation.