Distribution and Environmental Risk Evaluation of Metals in Sediment Cores from Marmara Ere ˘ glisi Shelf, Marmara Sea, Turkey

摘要

This paper studies trace element contents in core sediments from Marmara Ereglisi on the northern shelf of the Marmara Sea.The main objective is to detect the concentrations of the selected elements (Al, As, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn) andhistorical evolution of sediment quality. The average concentrations of elements in mg/kg are 17,500 for Al, 5 for As, 70 forCr, 12 for Cu, 10,742 for Fe, 137 for Mn, 44 for Ni, 20 for Pb, 43 for V and 44 for Zn. The average percentages of the sand,silt and clay fractions are 17%, 36% and 47%, respectively. Based on contamination factor, enrichment factor and pollutionload index, computed from carbonate-free metal values, the core sediments are unpolluted for Al, Cr, Cu, Fe, Mn, Ni and Vfor the entire length of the cores and moderately polluted for As, Pb and Zn in the upper parts of the cores. The relative metalenrichment in cores starts at core depths of 13 to 39 cm depending on sedimentation rates, which commonly increase fromthe outer shelf toward the coast. Considering the sedimentation rates, the metal pollution on outer and inner shelf areas startedabout 400–500 years ago. Contamination of the northern shelf sediments is insignificant compared to those of the southernshelf, the semi-enclosed bays and gulf areas of the Marmara Sea with large catchment areas having a high population densityand agricultural activities, as well as with similar marine shelf areas elsewhere in the world. This is mainly due to the smallcatchment area and the dynamic circulation system of the Marmara Ereglisi Shelf area.