The sorption behavior of dibenzothiophene on marine sediments treated by a sequential procedure was investigated. Sorption isotherms for dibenzothiophene on both no treatment and NaOAc-HOAc treatment sediments were all linear. Differences in Kp's between no-treatment and NaOAc-HOAc treatment sediments were mainly the result of differences in organic carbon content. Nonlinear adsorption isotherms of dibenzothiophene were observed on the sediments treated with H2O2 and could be described by the Freundlich equation. Nonlinear isotherms suggested that the sorption mechanism was a heterogenous adsorption process occurring on the surfaces of the residual organic matter and the bare inorganic minerals in the sediment. A linear correlation was found between the Freundlich constant K and the residual organic carbon. In addition, the clay content in the sediment also had a significant effect on the residual organic carbon content and the Freundlich constant K. Differences in the isotherms of dibenzothiophene between the H2O2 treatment sediments and the no or NaOAc-HOAc treatment sediments indicated that the sorption was strongly influenced by the change in composition as well as by the percentage of organic matter in the sediments. Copyright 1997Academic Press