SUMMARY
The article considers biogeochemical features of accumulation, redistribution and migration of heavy metals in bottom sediments in the conditions of oil pollution of coastal water areas. The Black Sea, like other parts of the world's oceans, is characterized by an increased content of pollutants in the coastal zone. The purpose of the study was to study the influence of the anthropogenic factor on the biogeochemical features of the bottom sediments of the coastal zone of the Black Sea. The research project is the bottom sediments of the Sevastopol Bay, as zones with increased anthropogenic load. For comparison, samples selected in the clean coastal zone of the Karadag Nature Reserve were used. Selection of the surface layer of bottom sediments was carried out according to a standard procedure. Samples were selected in 2013. The mineral composition of the selected samples was evaluated from x-ray phase analysis data. Concentration of chemical elements in samples was determined on mass spectrometer with inductively coupled plasma (ICP-MS) in the M.P. Semenenko Institute of geochemistry, mineralogy and ore formation of the National Academy of sciences of Ukraine. The investigated sediments are represented by sands with an insignificant content of clay fraction. The sand fraction is mainly represented by crystals of calcite, quartz and feldspars with an admixture of amorphous silica particles. The mineral composition of the silt fraction of bottom sediments is represented by clay minerals – montmorillonite, kaolinite, illite, and also finely dispersed calcite and quartz. The amount of organic substances did not exceed 1–1.5%. A significantly larger amount of organic matter was accumulated in the clay fraction of the bottom sediments of the Sevastopol Bay and amounted to about 3%. A distinctive feature of the silt of the Sevastopol Bay is the high degree of contamination with organic substances. The presence of clay minerals has a significant effect on the absorption of oil products by silt deposits. The influence of these processes on the microbiological composition of bottom sediments was investigated. It is shown that the natural biological processes of destruction of organic substances, leading to the formation of humic compounds, cause the fixation of heavy metals on these products and lead to a change in the microbiological composition of bottom sediments, which can disrupt the ecological balance of coastal water areas. The features of the content and distribution of microorganisms (aerobes, anaerobes and heterotrophs) are largely related to the physico-chemical properties of bottom sediments, the features of adsorption, sedimentation and accumulation of various metals in mud.