Heavy metals in sediments of the Black Sea

Abstract

The Black Sea is a semi-enclosed marine basin in the north of Turkey. It is almost in astate of isolation, if we exclude the connection to Mediterranean through the Aegean Sea and the Sea of Marmara. Due to its unique properties, it has been the subject of manystudies.This study̕s aim is to investigate the concentrations of metals such as Fe, Mn, Pb, Zn,Cu, Ni, Cr and Co in the sediments of the Black Sea and evaluate the metal contamination with Al normalization. For the study, the Black Sea Unit 1 sediments were collected from 7stations during the 2003 R/V Knorr Black Sea Cruise, Leg 2 and 3, which are conductedbetween April 25-May 10 and May 10-May 15, respectively. Fe, Mn, Pb, Zn, Cu, Ni, Cr,Co and Al concentrations of sediments obtained from these cruises were determined by atomic absorption spectrometry after total digestion. Hg contents of sediments from threestations were determined by flameless atomic absorption spectrometry after digestion.Experimental results were compared by different ways. Firstly, the metal distributionsand metal/Al normalizations along the cores at each station were investigated. Secondly, comparison of three stations which are located different part of Black Sea was made, inorder to see how the metal concentrations of the cores change from western to eastern partsof Black Sea. Finally, the results of these examinations were compared with the previousstudies.Generally, Mn and Fe concentrations are below the average shale Mn and Fe concentrations. Mn and Fe values show a sudden decrease in anoxic conditions, due to thediffusion to oxic layers throughout the cores.The high Pb contents at the top of the cores from stations which are close toBosphorus may most probably suggest a combination of diagenetic and anthropogeniceffects. Pb/Al ratios in all stations have an increase in the beginning of the cores, which isan indication of pollution.v Hg concentrations which obtained from three stations are generally below the averageshale Hg concentration. Hg/Al ratios are higher in the station which is the closest to theBosphorus. That is an indication of the pollution. High Hg/Al ratio is the consequence ofincreased anthropogenic activities in the vicinity of the Bosphorus Black Sea coastal areas that are urbanized and industrialized.Previous data and results obtained from this study show an increase in Pb, Zn, Cu, Niand Cr contents in the eastern surface sediments. This is because of the metal rich rocks incoast areas and associated economic mineral deposits in the catchment areas of rivers. In addition to this, high Hg/Al and Pb/Al ratios in south western surface sediments indicate ananthropogenic input from industrialized and urbanized regions.