The role of carbonate and organic matter in the sorption and desorption process of polycyclic aromatic hydrocarbons (PAHs) was studied by using a sequential separation procedure, which sequentially removed carbonate and organic matter from the natural sediment. Five PAHs were used as multi-sorbate and their sorption and desorption characteristics in separated samples were investigated. The Linear, Freundlich and Langmuir models were applied to correlate the experimental data to reveal sorption characteristics of PAHs. The results showed that the sorption mechanism was neither complete adsorption nor partition procedure. The desorption mass of PAHs was very low for all the three sediment samples, especially for higher ring PAHs. It was discovered that carbonate mainly affected sorption and desorption process of lower ring PAHs due to its influence on the physical characteristics of sediment. Organic matter remarkably affected the behavior of higher ring PAHs in the sorption and desorption procedure by determining the dominating partition process. (C) 2007 Elsevier B.V. All rights reserved.