Heavy Metal Distribution, Sources and Contamination Assessment in Polluted Marine Sediments: Keratsini Outfall Sewer Area, Saronikos Gulf, Greece

The central sewer of Athens had been discharging untreated sewage from 1950 until 1995 in the marine area between the island of Psyttalia and Keratsini. As a result, a surficial layer of organic mud was formed covering the seafloor. To assess the spatial and temporal distribution of metal contaminants in the area, six sediment cores were collected and analyzed for grain composition, organic carbon content (Corg), and metal concentrations. ICP-MS and AAS were used to determine the following metal concentrations: Cu, Zn, Mo, Ag, Cd, Cr, Pb, Ni, Fe, As, Mn, and Co. Four different lithofacies were identified based on grain size and macroscopic observations. The contamination of the sediments was assessed according to Enrichment factor (EF), Geo-accumulation Index (I geo ), and Pollution Loading Index (PLI), the latter was used in order to assess the overall toxicity status of the sediments. Factor analysis was also performed in the heavy metal, Corg, and Ca datasets. R-mode factor analysis indicates at least three different pollution sources in the area, while Q-mode analysis indicates three different groups of sediment samples according to their pollution degree. The present work stands among others to contribute to the better knowledge of the environmental impact of urban wastes on the shallow marine sediments adjoining large cities areas.