Distribution of Trace Metals (Cr, Cu, Ni, Pb, Zn, Sr, Ti, Mn and Fe) in the Vertical Section of Bottom Sediments in the Sevastopol Bay (Black Sea)

Purpose. The work is purposed at studying the elemental composition of the bottom sediments vertical section, and at evaluating the spatial-temporal variability and intensity of the polluting elements accumulation in the cores of the Sevastopol Bay bottom sediments based on the expedition research data. Methods and Results. Sampling of the sediment surface layer (0-5 cm) and cores was carried out in May, 2016 at four stations in the Sevastopol Bay water area along the following fairway: in the apex of the eastern part near the Inkerman CHP, in the central part, in the Yuzhnaya Bay and in the western part of the Sevastopol Bay. The sediment columns were divided into the layers of 1-2 cm thickness. To determine macro- and micro-element concentrations, each sample was dried and homogenized. The total content of elements was determined by the X-ray fluorescence analysis (XRF) using a "Spektroskan MAKS-G" spectrometer. The organic carbon (C-org) concentration in a sample was defined by the spectrophotometric method after the organic matter had been oxidized by a sulfochromic mixture. To assess contribution of the anthropogenic sources to the bottom sediments pollution relative to the average composition of trace elements in the earth crust, such indicators as the enrichment factor and the geoaccumulation index were used. A significant at the 95%-level positive correlation (0.6-0.9) between the distribution of the studied metals and the sediments geochemical features was revealed using the example of the C-org concentrations. Conclusions. Analysis of the obtained results of the EF parameter showed that the level of the bay bottom sediments enrichment with trace metals increased from moderate (4) and moderate-heavy (5) in the eastern apex to very heavy (27) and extremely heavy (90) ones in the Yuzhnaya Bay. It has been established that the maximum metal concentrations were associated with the periods of intense technogenic loads in the second half of the 20th century; as for Cu, Zn, Cr, and Fe, their concentrations continued to grow up to 2016. The content of lead and zinc in sediments decreased, while copper, on the contrary, increased up to 2016. Thus, the level of anthropogenic load on the Sevastopol Bay water area has not decreased, but even continues to grow.