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

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.