Biodegradation and Adsorption of Linear Alkylbenzene Sulfonates (LAS) in the River Environment

A Case Study on River Akashi of Hyogo Pref.

Abstract

The behavior of LAS in river waters was investigated in a medium-size river of Hyogo Pref. in November 1985 and March 1986. The LAS concentration was high in lower streams traversing urbanized areas and also relatively high in upper streams passing through newly developed housing districts. The distribution of LAS-assimilable bacteria was similar to that of LAS, and the correlation between the two concentrations was significant.
Four LAS homologues with C₁₀ to C₁₃ alkyl chain were detected in river waters. The relative abundance of LAS homologues is governed by “the distance principle” (SWISHER, 1963), according to which biodegradation of LAS is facilitated by increasing the distance between a sulfonate group and the most remote end of the alkyl chain.
The change of the relative abundance of LAS homologues was closely related with the increase of SS concentration in the middle reaches of the river. A laboratory experiment showed that the relative abundance of LAS homologues with longer alkyl chain decreased with as adsorption of total LAS onto SS took place. These results suggest that both adsorption on SS and biodegradation play an important role in the change of LAS composition in the river water.