Hydrocarbons in bottom sediments during a seasonal flood 2005 in the Dvina River estuary

The results of studying hydrocarbons during the flood in May 2005 are discussed. The concentration of aliphatic and polycyclic aromatic hydrocarbons are shown to match their concentrations in water areas with steady input of pollutants. Weathered oil and pyrogenic compounds dominated in their composition. The geochemical barrier the Northern Dvina River-Dvina Gulf is shown to become a filter during floods and prevents pollutants from penetrating into the White Sea.

Organic geochemistry of Late Cretaceous to Paleogene sediments from MITI Sanriku-oki borehole

Perylene is present in high concentration in Paleogene sediments from the Sanriku-oki borehole of the Ministry of International Trade and Industry (MITI), northeastern Japan. The borehole penetrates a thick sequence of Late Cretaceous to Neogene sediments deposited under a range of conditions, including fluvial-deltaic and shallow marine. Organic petrological and geochemical data show the sediments to be rich in organic matter (OM) derived from higher plants. Biomarker analysis of aliphatic and aromatic hydrocarbons confirms a significant input from higher plants, with extracts dominated by numerous gymnosperm- and angiosperm-derived biomarkers such as diterpanes, oleanenes, des-A-triterpanes and their aromatized counterparts. The highest concentration of perylene occurs in Middle Eocene sediments deposited in a relatively reducing environment. Stable carbon isotope compositions show 13C enrichment in perylene compared to gymnosperm and angiosperm biomarkers, consistent with a fungal origin. This elevated abundance of sedimentary perylene could relate to a Paleogene continental climate where fungi probably flourished.

Alkane and hydrocarbon concentrations of ODP Leg 104 sites

Sedimentary extractable organic matter was analyzed at three ODP Leg 104 sites in the Norwegian Sea. Organic carbon content ranged from less than 0.1% to a maximum of 1.8%. Extractable organic matter content and unresolved complex mixture concentrations were low and randomly distributed. Low levels of aliphatic (branched and normal) and aromatic hydrocarbons were detected in all of the sediments analyzed. Total aliphatic and aromatic hydrocarbon concentrations ranged from 176 to 3,214 and 6 to 820 ppb, respectively. The concentrations of individual aliphatic (n-C15 to n-C32) and aromatic (two- to five-ring) hydrocarbons were generally less than 50 ppb and less than 10 ppb, respectively. No significant trend with sub-bottom depth was observed in either bulk organic matter or individual hydrocarbon concentrations. The predominant source of Cenozoic sedimentary hydrocarbons is concluded to be ice-rafted debris from the adjacent continent. All sites contain a mixture of recycled, mature petroleum-related and terrestrially derived hydrocarbons.

Migration forms of hydrocarbons in waters and bottom sediments of the Gulf of Riga

It is found that hydrocarbons are constantly accumulated on the main geochemical barriers: water-atmosphere, river-sea, water-suspended matter, and water-bottom sediment interfaces. Degree of hydrocarbon accumulation reaches 13.5-17.6 in the surface microlayer and exceeds 1000 in bottom sediments. Hydrocarbon composition changes in this process. Local pollutant loads result in accumulation of polycyclic aromatic hydrocarbons by bottom sediments and benzo(a)pyrene concentration sometimes exceeds MPC. Content of hydrocarbon migratory forms is calculated.