Assessment of technogenic and natural hydrocarbon supply into the Black Sea and seabed sediments

The nature of hydrocarbons in the marine environment of the Black Sea is quite diverse: syngenetic biochemical gases, deep epigenetic gases and technogenic hydrocarbon components. The level and contribution of hydrocarbons from these sources to the marine environment are evaluated in this paper. etic hydrocarbon components are represented by biogenic methane. Methane concentrations reach their maximum in the hydrogen sulphide zone. It is established that there is a high rate of methane generation in seawater and seabed sediments. High gas saturations in seabed sediments produce acoustic anomalies (BSRs, bright spots, “boiling” sediment, griffons, etc.). ydrocarbons are associated with gas evolution (seepage). To date more than 65 underwater mud volcanoes have been mapped in the Black Sea. Biogenic production of methane is higher than the flow from seeps by approximately 1.5 times. Considerable quantities of hydrocarbons are contained in accumulations near mud volcanoes; gas hydrates are also associated with them. Thus, it follows that hydrocarbons are natural components of the Black Sea, and they are the part of a single biogeochemical cycle of carbon in the marine environment. genic hydrocarbon components are supplied to the sea from onshore by river catchments, industrial activity at oil-loading terminals, tanker transportation and marine navigation. Technogenic contamination is also noted in the coastal zone of the sea in general. Commensurate discharges to the marine environment of petroleum hydrocarbons of natural and technogenic origins can be recognized.