Proceedings of the Eight International Conference on the Mediterranean Coastal Environment MEDCOAST07, E. Özhan (Editor), 13-17 November 2007, Alexandria, Egypt On Formation of Perylene in Sediments from Gulf of Gemlik, Turkey Selma Ünlü (1) and Bedri Alpar (1,2) (1) Istanbul University, Institute of Marine Science and Management, 34116 Vefa, Istanbul, Turkey Tel: + 90-212-440 00 00/26087, Fax: + 90-212-526 84 33 E-mail: su@istanbul.edu.tr (2) E-mail: alparb@istanbul.edu.tr Abstract Perylene is a polycyclic aromatic hydrocarbon (PAH) that has been found widely in a variety of depositional environments and riverine sediments. It is the most important diagenetic PAH and also produced by in situ degredation of biogenic precursors. Meanwhile, anthropogenic perylene in the aquatic systems could be introduced via terrestrial runoff or airborne particulates and different emission sources. High abundances of perylene relative to other PAHs can indicate origin of the compound. In this study, surficial sediments from Gulf of Gemlik, Turkey were analyzed for special PAH compound ratios, such as Perylene/ΣPAHs, Perylene/Penta- aromatic isomers, Pyrene/Perylene, Benzo(e)pyrene/Perylene using gas chromatography-mass spectrometry. Having a wide range of concentrations (0.1 to 485 ng/g, dry weight), the highest concentrations of perylene were observed in Gemlik harbour, its anchoring areas, near shore cable and petroleum plants at Güzelyalı, close to urbanized towns in the south (Mudanya, Kurşunlu and Trilye) and even some resorts areas along the northern coast. High concentrations of perylene relative to penta- aromatic isomers, as detected between 10-75%, indicate diagenetic origin for the presence of perylene. Low level of perylene might have been derived from the anthropogenic inputs, caused by either local effluent or atmospheric dry deposition.