The sources of metal contents in the shelf sediments from the Marmara Sea, Turkey

The shelf area is the largest morphological unit of the Marmara Sea and is subjected to increasing population, urbanization, and industrial activities. Metal contents (Al, Fe, Mn, Cu, Pb, Zn, Ni, Cr, Co and Hg) of the surface sediments from the shelf areas of the Marmara Sea generally do not indicate shelf-wide pollution. The variability of the metal contents of the shelf sediments is mainly governed by the geochemical differences in the northern and southern hinterlands. Northern shelf sediments contain lower values compared to those of the southern shelf, where higher Ni, Cr, Pb, Cu and Zn are derived from the rock formations and mineralized zones. However, besides from the natural high background in the southern shelf, some anthropogenic influences are evident from EF values of Pb, Zn and Cu, and also from their high mobility in the semi-isolated bay sediments. Anthropogenic influences are found to be limited at the confluence of Istanbul Strait in the northern shelf. However, suspended sediments along the shallow parts of the northern shelf were found to be enriched in Pb and Hg and to a lesser degree in Zn, reflecting anthropogenic inputs from Istanbul Metropolitan and possibly from the Black Sea via the Istanbul Strait.