Contribution ratio of freely to total dissolved concentrations of polycyclic aromatic hydrocarbons in natural river waters

► The ratios of freely to total dissolved concentrations of three polycyclic aromatic hydrocarbons (PAHs) were studied. ► The ratio sequence of the three PAHs was phenanthrene > pyrene > chrysene. ► The ratios were significantly negatively correlated with the log Kow (octanol-water partition coefficient) values of PAHs. ► The ratios were negatively correlated with suspended sediment and dissolved organic carbon concentrations in river water. ► Characteristics of suspended sediment and dissolved organic carbon were also important factors affecting the ratios.