Heavy metal concentrations (Zn, Cu, Pb, Cd) in sediments of the southwest Caspian Sea Basin (Astara to Kiyashahr)

Abstract

Heavy metals Zn, Cu, Pb, Cd concentration in sediments of the Iranian waters of the Caspian Sea was measured in fall 2001.Samples were collected from transects along the Iranian coastline in five stations lying between Astara (48 52', 38 26') up to Kiyashahr (49 53', 37 27'). Metals were extracted from sediments by digesting with hydrofluoric and hydrochloric acid. Metals concentrations were measured using the Atomic Absorption Spectrophotometer. Reliability of results was tested using Soil-7, a certificated reference material (CRM). Sediment samples were also collected from each station to determine grain size. The results showed that except for Cd concentration which was measured at 4.5kg g super(-1) dry weight, other values were lower than the Effects Range Low (ERL) (1.2kg g super(-1) dry weight) based on the Sediment Quality Guidelines from NOAA, USA for Cd. Also, the highest concentration determined for Cu (19.55kg g super(-1) dry weight) in this study was lower than the ERL (34kg g super(-1) dry weight) value determined by NOAA for Cu. The highest concentrations for Pb and Zn in the present study were 25.7kg g super(-1) dry weight and 54.5kg g super(-1) dry weight, respectively that were lower than the ERL values (Pb = 47kg g super(-1) dry weight and Zn = 124kg g super(-1) dry weight) declared by NOAA for these metals. It is evident from the present study that heavy metals concentrations in sediments in the study area were lower than Effects Range Low values for these metals. We conclude that the studied metals are not threatening to the environment at the present time.