Material and energy flows in the marginal filters of rivers identified based on the analyses of the environmental fate of polycyclic aromatic hydrocarbons (PAH): Anthracene (An), Phenanthrene (Phen), Naphthalene (Naph), Pyrene (Py), Fluoranthene (Flu), Chrysene (Chr), Benzo[a]pyrene (BaP), Perylene (Pl). Experimental data on the components of the aquatic system of the marginal filter of the Northern Dvina River allow us to consider the processes of phase transitions of PAHs at geochemical barriers (GCB). Based on the principles of thermodynamics, a phenomenological model of migration and the formation of the most persistent PAH associations on the barriers is formed. The predominant possibility of PAH migration on suspended material, including biota, is shown. The probability of PAH accumulation between the most important components of aquatic systems was assessed according to the conditions of their migration activity in various zones of the marginal filter. Active and passive PAHs were determined in terms of their migration and accumulation in the components of aquatic systems. The role of PAHs as a reliable indicator of thermodynamic processes, including the development of technogenesis, is estimated. © 2020 The Authors, published by EDP Sciences.