Immobilized Enzymes and Heavy Metals in Sediments of Venice Internal Canals

Abstract

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 observed over background values: up to 41 for mercury, to 17 for Zn, to 7 for Cd and Pb. A significant relationship was found between metal (Hg) concentrations and the content of fine fraction (<63µm) in the sediment. Sediments of the Venice rii were shown to be very rich in enzymes 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 enzymatic point of view, the behaviour of sediments of Venice internal canals was qualitatively and quantitatively more similar to a septic tank than to the sediments of other areas of the surrounding lagoon. The relationship between protease activity and mercury content was also investigated and found to be correlated.