A Survey of Heavy Metal Concentrations in the Surface Sediments along the Iranian Coast of the Caspian Sea

Abstract

Metals discharged into coastal areas of marine environments are likely to be scavenged by particles and removed to the sediments. The sediments, therefore, become large repositories of toxic heavy metals. This research examined the concentrations of heavy metals (Al, Cd, Cu, Pb, Ni, Zn) in the nearshore sediments in the alongshore direction of the Iranian coast of the Caspian Sea. Fourteen samples were collected and granulometric compositions were determined. The consideration of three grain size fractions (0.355 mm, 0.212 mm and 0.075 mm), plus fourteen bulk samples required analyzing 56 samples for the presence of heavy metals. Laboratory analysis of the samples was accomplished using the Cold Acetic Protocol, followed by Inductively Coupled Plasma Optical Emission Spectroscopy. Preparation of the samples involved the utilization of the Cold Acetic Acid Extraction Protocol established by the Great Lakes Institute for Environmental Research (GLIER), Canada. The results provided evidence of large differences in total metal concentrations in the sediment samples from the fourteen sites. Box and Whisker plots demonstrated that metal concentrations were not homogeneously distributed, and that there were large spatial variations in the median concentrations of heavy metals at each sample site. The statistical technique of discriminant analysis revealed that the six heavy metals had distinct and statistically significant concentrations at various locations along the coast. Concentrations reflected metal loadings from anthropogenic sources located at and in the vicinity of the sampling sites