Determination of heavy metal (Cr, Zn, Cd and Pb) concentrations in water, sediment and benthos of the Gorgan Bay (Golestan province, Iran)

The coastal area of the Caspian Sea and Gorgan Bay are important ecosystems receiving discharge from their tributaries. In this study, concentration of lead (Pb), cadmium (Cd), zinc (Zn) and chromium (Cr) was seasonally determined at 8 sampling points during 2009-2010. Water samples were collected from the sampling stations and transferred to laboratory in polyethylene containers, whereas, sediment and benthic fauna samples were collected using a Van Veen grab. The levels of heavy metals were determined by atomic absorption spectroscopy method. Results showed that range of Pb, Cd, Cr and Zn in the water samples were 80-123, 61-97, 63-87 and 82-120 ppb, respectively; and their ranges in the sediment samples were 479-1072, 98-293, 102-622 and 937-1577 ppb, respectively. The range of Pb, Cd, Cr and Zn in the benthos samples were 95-132, 59-110, 26-58 and 103-155 ppb, respectively. Zn and Pb were the most concentrate metals in all samples. Likewise, sediment had the highest heavy metal content amongst the samples. This study demonstrated that the level of metals in the environment is increasing, bringing a serious warning to industries and threat of man-made contamination, which can be restricted and a necessity to control ecosystem and food-chain pollution