IMMOBILIZED ENZYMES AND HEAVY-METALS IN SEDIMENTS OF VENICE INTERNAL CANALS

Sediments of internal canals (rii) of Venice's historical centre, were analyzed for the concentrations of heavy metals (Hg, Cu, Ni, Co, Cd, Pb, Zn, Fe) and for enzymatic activity. Enrichment factors were observ ed over background values: up to 41 for mercury, to 17 for Zn, to 7 fo r Cd and Pb. A significant relationship was found between metal (Hg) c oncentrations and the content of fine fraction (< 63 mu m) in the sedi ment. Sediments of the Venice rii were shown to be very rich in enzyme s capable of hydrolysing proteins, polysaccharides, urea and phosphate derivatives at a surprisingly high rate. Enzymes were associated with the particulate matter rather than the pore-water phase. From the enz ymatic point of view, the behaviour of sediments of Venice internal ca nals was qualitatively and quantitatively more similar to a septic tan k than to the sediments of other areas of the surrounding lagoon. The relationship between protease activity and mercury content was also in vestigated and found to be correlated.