ORGANIC-CARBON AND NITROGEN IN SEDIMENTS AND IN RESUSPENDED SEDIMENTS OF VENICE LAGOON - RELATIONSHIPS WITH PCB CONTAMINATION

The distributions of organic carbon and nitrogen in sediments and in resuspended sediments obtained by resuspension experiments on undisturbed sediment cores from Venice Lagoon, were investigated in July 1987. Shear stresses which can be produced by wind waves during storms were used. Organic carbon ranged 8.6-27.3 mg g-1 in resuspended sediments and 5.2-14.6 mg g-1 in sediments. Organic nitrogen ranged 0.95-3.70 mg g-1 in resuspended sediments and 0.30-0.92 mg g-1 in sediments. At every station, resuspended sediments had a C/N atomic ratio lower than that of the corresponding underlying sediment. This is ascribed to a lower decomposition degree of organic matter in resuspended sediments. The composition of organic matter appears to play an important role in determining the accumulation of PCBs in resuspended sediments. The surprisingly high level of these contaminants in resuspended sediments at a large distance from the contamination source may be ascribed to a contribution of animal materials.