Anthropogenically derived mercury in sediments of Pialassa Baiona, Ravenna, Italy

Pialassa Baiona, a coastal wetland near the city of Ravenna, has been impac ted for two decades (1958-1978) by industrial discharges containing mercury and floating agglomerates of residues of polymerization processes. Althoug h the industrial use of mercury completely, ceased in the early 90's, surf- ace sediments are still highly contaminated, mercury concentrations! decrea sing from the southern subbasin, close to the discharge point, to the farth est northern border. Concentrations of total mercury, synthetic polymers (d etermined by pyrolysis-GC/MS), total organic carbon, C/N ratio, total sulfu r and Pb-210 dating, were determined in sediment cores collected in the sou thern and northern sub-basins. Mercury and polymers exhibited parallel prof iles with a peak corresponding to the historic emission record in the south ern core, while in northern cores peaks of maximum concentration display a delay reflecting the time required for the pollutants to migrate. A recentl y developed mercury sequential extraction procedure was applied to the most polluted layers to study inorganic mercury speciation. Results indicate di fferences between the southern and northern areas, suggesting a more effici ent binding of mercury to sediments in the southern sub-basin.