Distribution and Composition of Hydrocarbons in the Bottom Sediments of Kamyshovaya Bay (Black Sea)

Purpose. The purpose of the study is to identify the features of spatial and vertical distribution of hydrocarbons in bottom sediments of the coastal area under constant anthropogenic load, and to assess the likely sources of their inlet into the marine environment (using Kamyshovaya Bay as an example). Methods and Results. The surface layer of bottom sediments (nine stations) and the sediment column were sampled in July 2021 as a part of long-term monitoring of the Sevastopol bays jointly performed by FRC IBSS and FRC MHI. The features of spatial distribution of hydrocarbons, alkanes and some geochemical markers in the surface layer (0-5 cm) and the vertical profile of bottom sediments are studied. The 30-year accumulation history of the considered substances in the bay bottom sediments is analyzed. The concentration of hydrocarbons in the bottom sediments ranges from 27.6 to 98.5 mg/kg that allows us to classify these sediments as low-polluted. A layer-by-layer study of the hydrocarbon composition in the bay bottom sediments shows that in the course of 30 years the bottom sediments were not significantly polluted with hydrocarbons. The results of analyzing the alkane composition and the geochemical marker values make it possible to establish that, as well as in the surface layer, the predominant source of hydrocarbon inlet was allochthonous and autochthonous organic matter. The increased values of geochemical markers identifying oil pollution indicate the fact that the inlet of oil and oil products can be considered a secondary source of hydrocarbons. Conclusions. Hydrocarbons in the bottom sediments are distributed unevenly over the Kamyshovaya Bay water area, namely in the central part of the bay, a zone of the increased pollution is formed. It can be a consequence of the processes taking place in the semi-enclosed bay, as well as conditioned by the type of bottom sediments. The results of studying the hydrocarbon composition of bottom sediments show that in the course of the past 30 years and up to the present, Kamyshovaya Bay has been under the anthropogenic load which fluctuated insignificantly due to the degree of economic activity of the port. At the same time, the level of pollution in the bay remains low.