Distribution and sources of hydrocarbons in surface sediments of Gemlik Bay (Marmara Sea, Turkey.

Abstract

Sea bottom sediments from Gemlik Bay, one of the most polluted spots in the SW Marmara Sea, were analyzed for parent polycyclic aromatic hydrocarbons (PAHs) using gas chromatography-mass spectrometry. The concentration of 14 PAH compounds in sediment samples collected from 61 locations are distributed in a broad spectrum from low to very high concentration levels (50.8–13482 ng g 1). No significant correlation was found between PPAHs and organic carbon content while PPAHs increase slightly with silt/clay ratio. Therefore the distribution and concentrations of PAHs would be determined more by direct input, rather than by the type of sediment found locally. The most polluted areas are distributed nearshore eastern (Gemlik) and southern (Kursunlu, Mudanya, and Trilye) coasts which are mainly influenced by rapid ecotourism development, direct discharges from rivers, surface run off and drainage from portareas, domestic and industrial effluent discharges through outfalls and various contaminants from ships. Special PAH compound ratios, such as Phe/Anth, Flu/Py, B[a]A/Chry; LMWPAH/HMWPAH; Per/; Per/P(PAH); Per/P(penta-aromatics) and Flu/(Py + Flu), were calculated to evaluate different hydrocarbon origins and their relative importance. Pyrolytic activity is dominant along the highly-populated eastern and southern coasts. Meanwhile, petrogenic activity mixed with pyrolytic activity is a matter of fact in front of the main industrial–tourism ports and anchoring areas as well. The higher concentration of perylene is distributed along with the most polluted eastern and southern coastal areas, however, the concentrations of perylene relative to the penta-aromatic isomers are dominant especially in the northern and deepest sectors of the bay, indicating diagenetic origin for the presence of perylene