Saturation phenomena for the uptake of polynuclear aromatic Ž . hydrocarbons PAHs by rooted aquatic plants were observed in both field and laboratory experiments. From these data, a Langmuir adsorption model was derived and was shown to describe the assimilation of sediment PAHs by aquatic plants at low-sediment PAH concentrations. The low-concentration restrictions were relaxed by using an empirical Freundlich model. This permitted the specification of equilibrium constants, relative rate constants for adsorption and desorption, and saturation levels, and it provided a realistic description of the acropetal mobilization of sediment PAHs by rooted aquatic macrophytes. The growth of aquatic plants was found to be inhibited by sediment PAHs, but at concentrations several orders of magnitude above the corresponding threshold effect levels for aquatic animals. The effects of the acropetal transport of sediment PAHs into the above-soil portions of aquatic plants merits further investigation because of the possibility of an enhanced availability of these carcinogens to associated aquatic food webs. In addition, these results may suggest pathways for bioremediation of the impact of PAHs on associated biota.