Environmental impact on the surface sediments of the bay and the gulf of Thessaloniki (Greece) according to the geoaccumulation index classification

Abstract

The area under investigation is the gulf and the bay of Thessaloniki which comprise the northern part of Thermaikos gulf. During the last years the area is being loaded with heavy metals and organic pollutants coming from industrial and domestic discharges of Thessaloniki city. As a result of the anthropogenic activities, the seabed properties are changed and moreover the marine ecosystem is disturbed. The aim of the study was to determine the environmental impact on the surface sediments so that the extent of heavy metal pollution is quantified and the whole area could be characterized according to the geoaccumulation index (Igeo). For this purpose, thirty three sediment samples were collected from the bay and the gulf of Thessaloniki. The diameter <2 μm sediment fraction of the samples was analyzed for the heavy metal content (Zn, Cu, Ni, Cr, Pb, Cd, Fe and Mn). The geoaccumulation index was then calculated comparing the concentration of the respective elements to that of unpolluted sediments, the so called `background value'. According to the Igeo classification, the bay of Thessaloniki was characterized as moderately polluted to strongly polluted for the metals Zn, Cd, Pb and unpolluted to moderately polluted in Cu, Ni and Cr, while the gulf of Thessaloniki was characterized as an unpolluted to unpolluted to moderately polluted marine area.