Distribution and accumulation of polycyclic aromatic hydrocarbons in terrestrial-aquatic interface environments

Human settlements and industrial activities located near coastal zones, together with intensive navigation, contribute to the accumulation of hazardous polycyclic aromatic hydrocarbons (PAHs). Research on the distribution of pollutants in shoreline depositional environments has been limited mainly to the accumulation of PAHs in soils and bottom sediments, while overlooking shoreline deposits as a crucial intermediate barrier zone formed at the interface between aquatic and terrestrial systems. High-performance liquid chromatography was employed to analyze the distribution of priority PAHs in soils, shoreline deposits, and bottom sediments of a coastal area subjected to different types of anthropogenic impact, using the Lower Don River and the Taganrog Bay in southern Russia as a case study. Results indicate that, in terms of total polyarene content, the depositional environments form the following sequence: soils 126-4305 ng/g > bottom sediments 105-3277 ng/g ≈ shoreline deposits 173-3027 ng/g. The composition of high-molecular-weight PAHs varies depending on pollutant sources and the position of the depositional environment. At the water-land interface, shoreline deposits demonstrate considerably higher accumulation of fluorene and phenanthrene and lower accumulation of BbF compared with soils and bottom sediments. In depositional environments of automorphic positions, the share of high-molecular-weight compounds within the sum of 15 PAHs increases under the influence of aerotechnogenic sources. As the landscape position of the depositional environment decreases, liquid fuel spills become the dominant source of pollutants, resulting in a higher proportion of low-molecular-weight compounds among the sum of 15 priority PAHs.