Polycyclic Aromatic Hydrocarbons in the Bottom Sediments of the River – Sea Mixing Zone on the Example of the River Chernaya and the Sevastopol Bay (the Black Sea)

Purpose. The study is aimed at determining concentrations of the polycyclic aromatic hydrocarbons (PAHs) and at revealing their pattern distribution in the bottom sediments of the "river – sea" contact zone on the example of the Sevastopol Bay and the river Chernaya. Methods and Results. Granulometric composition of the bottom sediments was determined by the decantation and dispersion method. Identification and quantitative determination of PAHs were carried out by the high performance liquid chromatography method. The total PAHs content in the bottom sediments of the area under study varied from 12 to 670 ng/g of dry weight. The pollutant content was minimum in the river site beyond the geochemical barrier. In the area where the river Chernaya flows into the Sevastopol Bay, the PAHs content was 121 ng/g. The highest PAHs content was revealed in the Sevastopol Bay bottom sediments, more precisely, in 1.5 km southwest of the river Chernaya flowing into the bay. 14 PAHs were identified in the estuary zone of the river, 4 of them (naphthalene, 2-methylnaphthalene, fluorene, anthracene) were in the trace amounts. The maximum concentration (99%) of silty material was observed in the Sevastopol Bay water area. The silt fractions were distributed as follows: 20% – aleuritic-pelite fraction, 79% – pelitic-aleurite fraction. Directly in the area of the river inflow into the bay, accumulation of the sand fraction (7%) and the maximum portion of pelitic silts were noted. Conclusions. The recorded values of PAHs corresponded to the natural non-toxic levels. PAHs identified in the bottom sediments of the river estuary zone are of the mixed, predominantly petrogenic origin. The obtained data show that in the conditions of the "river – sea" contact zone, the PAHs accumulation in general and their individual fractions were governed mainly by presence of silt in the bottom sediments.