Sea sediments contaminated with heavy metals: metal speciation and removal

The contamination of sediments with heavy metals may lead to serious environmental problems and in some cases action has to take place for their decontamination. In this work, studies were performed on sediments near the outfall of domestic and industrial waste. The metals examined were Cu, Cr, Ni, Pb, Zn and Fe. Indeed, high metal content was found in the sediments and the contamination factors were quite high, indicating the effect of the nearby discharge of effluents. The results of the application of a sequential extraction partitioning procedure indicated that an important part of the metal content is carried by the residual phase but also a significant percentage is found in the organic and reducible fractions, i.e. in potentially available fractions. Batch extraction experiments using acid solutions of various concentrations and different acid-sediment contact times were performed in order to remove heavy metals from the sediments. For most metals studied, a satisfactory percentage was extracted at low contact times.