Sources, distribution, and water column processes of aliphatic and polycyclic aromatic hydrocarbons in the northwestern Black Sea water

Aliphatic and aromatic hydrocarbons have been determined in (28 samples) su spended particulate matter (>0.7 mu m) collected at subsurficial seawater a nd three vertical profiles in a transect from the continental shelf, slope, and deep basin (15 samples) of the western Black Sea. The dissolved phase (>0.7 mu m) was collected at subsurficial and in the redoxcline (6 subsurfi cial and 5 deeper). The highest concentrations of hydrocarbons were detecte d in the Danube, Dnieper, and Dniester River Estuaries and other point sour ces of pollution located offshore Romania and Bulgaria where oil production and refining is carried out (i.e., Constantza, Varna). Concentrations of h ydrocarbons decreased with increasing distance from the coast, but relative ly high concentrations were found at the open stations where the particulat e organic carbon (POC) is higher. Fossil PAHs are predominant in the coasta l stations, and the unresolved complex mixture (UCM) of aliphatic hydrocarb ons is predominantly of a fossil common origin according to the hopane and sterane distribution. The fossil to pyrolytic PAH ratio decreases with sour ce distance attributable to a deposition of pyrolytic PAHs. The spatial dis tribution of PAHs found in the dissolved phase is evenly distributed. The u nresolved complex mixture/ alkane ratio is higher in the dissolved phase an d can be attributable to a faster degradation of labile n-alkanes in this p hase. Vertical profiles of hydrocarbons in suspended particles show two sub maxima located in the biomass maximum abundance and at the redoxcline where there is an enrichment referred to POC due to phytoplankton or bacteria up take, respectively.