The distribution of Cd and Cu in sediments covered with algal mat

Abstract

In coastal marine environments, with shallow, warm and calm waters, it is sometimes possible to observe the presence of organosedimentary structures that are commonly flat and laminar in shape. These structures are called algal mats or recent stromatolites due to their remarkable similarities to fossil stromatolites. The aim of this work was the study of the distribution of the various forms of Cu and Cd in the main layers of coastal algal mats in a closed bay at Anavissos, on the coast of Saronikos Gulf. Small sediment cores were collected from one point inside the cove on a seasonal basis and the trace metals extracted according to the BCR sequential extraction method. The main results of the study were: Most of the labile Cd was associated with small inorganic grains or lime particles. The contribution of the fraction associated with Mn and Fe oxides, was similar to that adsorbed to organic compounds and sulfides. The high contribution of the labile Cd to the total element (over 85%) was a strong indication of anthropogenic origin. On the other hand, most of the Cu in the sediment was associated with the crystal lattice (74%). Cu showed increased seasonal fluctuation; most of its labile forms were associated with organic compounds and sulfides whereas the less abundant form was that associated with Mn and Fe oxides. On the whole, the sediments were slightly enriched in Cd, while the concentrations of Cu were normal for the region.