TRACE METAL ENVIRONMENTAL CONTAMINATION RECORDS IN CORE SEDIMENTS OF GORGAN BAY IN THE SOUTHEAST OF THE CASPIAN SEA

In this study five sedimentary cores were collected from Gorgan Bay (southeastern part of the Caspian Sea). Concentrations of elements were measured to determine depositional trends and geostatistical assessment of toxic elements was carried out. Al, Fe, K, Mg, Na and S content increased in all 5 cores, from the bottom to near the top layer, with maximum concentrations at 15–45 cm depths. However, for the toxic elements, maximum concentration of As, Cr, Cu, Pb, Zn, Co and Ni varied in different depth of 5-15 cm and 80-120 cm. Enrichment factors (EFs) and pollution load index (PLI) were calculated to assess the enrichment and pollution of heavy elements in the bay sediments. Except for Ca and S, all studied elements showed positive and significant correlations with Fe and Al, which indicate the same source (human or natural). Principal component analysis (PCA) indicated that sediments were influenced by both geologic and anthropogenic impacts. According to the EFs, most toxic elements showed no significant enrichment and no pollution in the core sediments. Based on PLI average value in all cores, the southeast coast of the Caspian Sea (Gorgan Bay) should be classified as not metal polluted, but in recent decades there has been a dramatic increase of toxic elements that needs more attention and also