SHORT HISTORICAL REVIEW OF METAL SPECIATION AND DISTRIBUTION OF FIVE SELECTED METALS IN ADRIATIC SEA SEDIMENTSGuido Perin and Andrea Giacometti
Metals from natural sources found in the aquatic sediments are normally structured in complex mineralogical matrices and sometime can be released only by complete dissolution of sediments. Metals originated from industrial and urban pollution are bound to sediment in different geochemical phases having different bonding chemical energy. The determination of the speciation, i.e., the amount of metal associated to a specific phase, provides a good indication of the origin of the metal as well as its availability to the biota. The speciation criterion was applied to five metals, Cu, Cr, Pb, Ni, and Zn, in the course of a ten year research on sediment pollution of a large area of the northern Adriatic Sea. 228 stations were sampled and the results showed that large amounts of metals were originated from natural unidentified sources. The distributions of extractable heavy metals, i.e., those fractions available to the food webs, were greatly different with respect to the distribution of the Total Metal (TM) content. The authors conclude that to classify sediments in order to accurately evaluate the environmental risk it is necessary to update the old criterion based on TM with a new one based on the increasing extraction strength to determine the availability of a specific metal to the aquatic biota and therefore the effective toxicity.
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