Environmental Behavior of Alkylbenzenesulfonates in Tokyo Bay

Abstract

Environmental behavior study was carried out for alkylbenzenesulfonates (LAS) in Tokyo Bay and main rivers of its drainage basin. LAS represents a mixture of homologues having various alkyl chain lengths with isomers of varying phenyl position. The concentrations of each LAS homologue and 2-phenyl isomer in the environment, the influents and effluents of some sewage treatment plants, and some domestic detergents were analyzed using high performance liquid chromatography with fluorescence detection. The compositions of the LAS found in these samples were different among each sample and reflected biological or physicochemical processes which each LAS component was removed by. (1 ) About 90% of LAS was removed by sewage treatment. A shift toward shorter alk yl chain length in the residual as compared with the original LAS was quite apparent. The selective removal of 2-phenyl isomer during activated sluge treatment process also occurred. ( 2 ) After LAS had been discharged into the rivers, longer rchain, more sorpti ve LAS homologues and 2-phenyl isomer were relatively enriched in the river sediment.2-phenyl isomer was also removed by biodegradation. Thus average LAS chain length was found to be shorter and 2-phenyl isomer ratio to be poor in the river waters. ( 3 ) Longer chain LAS homologues and 2-phenyl isomer w ere abundant in the bay water samples in comparison with the river water samples or the effluent sewage samples. This can be explained by much release of the absorbed LAS from the river sediment and running into the bay as dissolved and suspended LAS by the rise of the rivers in heavy rainfall. Thus chemicals in river sediment may contribute to bay water pollution.