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Le rôle de la macrofaune dans la mise en liberté des sels nutritifs des sédiments de la lagune de Venise
No full textINFLUENCE OF WASTE-WATERS FROM THE CITY OF VENICE AND THE HINTERLAND ON THE EUTROPHICATION OF THE LAGOON
No full textFour seasonal samplings of lagoon waters were carried out during successive phases of high and low tide at stations located within Venice and its surroundings to monitor various physico-chemical parameters (pH, redox potential, temperature), salinity, nutrient concentrations (nitrogen, phosphorus, carbon compounds) and bacteria (total coliform bacteria). Salinity was used as a parameter for estimating the hydrographic distance from the Adriatic Sea, and for grouping stations into five homogeneous areas. A negative correlation was found between salinity and the concentrations of nutrients. Gradients of increasing concentrations of nutrients were observed at increasing hydrographic distance from the sea. The contributions to eutrophication of fresh waters entering the lagoon from the hinterland and of waste waters from the city have been estimated and found to be comparable. Some necessary interventions for the restoration of the lagoon are suggested. © 1990.Four seasonal samplings of lagoon waters were carried out during successive phases of high and low tide at stations located within Venice and its surroundings to monitor various physico-chemical parameters (pH, redox potential, temperature), salinity, nutrient concentrations (nitrogen, phosphorus, carbon compounds) and bacteria (total coliform bacteria). Salinity was used as a parameter for estimating the hydrographic distance from the Adriatic Sea, and for grouping stations into five homogeneous areas. A negative correlation was found between salinity and the concentrations of nutrients. Gradients of increasing concentrations of nutrients were observed at increasing hydrographic distance from the sea. The contributions to eutrophication of fresh waters entering the lagoon from the hinterland and of waste waters from the city have been estimated and found to be comparable. Some necessary interventions for the restoration of the lagoon are suggested. © 1990
Field resuspension of sediments in the Venice lagoon
No full textA portable device for measuring particle resuspension from undisturbed sediment cores has been used in different polluted areas of the Venice lagoon. By applying shear stresses reproducing the water turbulence generated by normal windy storm events in the lagoon, average resuspended matter (RM) amounts of 4.22 +/- 2.83 and 7.34 +/- 4.53 mg cm-2, respectively, were measured. As an average, the concentrations of C(org), N(tot) and P(tot) determined in the RM were 2-5 times higher than in the 5-cm surface sediments. Only minor nutrient increases were observed in the overlying waters after the shear stress applications.A portable device for measuring particle resuspension from undisturbed sediment cores has been used in different polluted areas of the Venice lagoon. By applying shear stresses reproducing the water turbulence generated by normal windy storm events in the lagoon, average resuspended matter (RM) amounts of 4.22 ± 2.83 and 7.34 ± 4.53 mg cm‐2, respectively, were measured. As an average, the concentrations of Corg, Ntota& d Ptot determined in the RM were 2–5 times higher than in the 5‐cm surface sediments. Only minor nutrient increases were observed in the overlying waters after the shear stress applications. © 1991 Taylor and Francis Group, LLC
Influence of Venice lagoon macrofauna on nutrient exchange at the sediment-water interface
No full textVenice Lagoon benthic macrofauna, in an experimental laboratory system (0.3 × 0.4 × 0.8 m), significantly affected nutrient exchange at the sediment-water interface. After macrofauna addition, the inorganic nitrogen release rate from the sediment increased by an order of magnitude compared with the values obtained in the undisturbed experimental system (from 1.7 to 23 mmol m-2 day-1), while a two- to three-fold increase was observed for reactive phosphorus (from 0.26 to 0.7 mmol m-2 day-1). In this system, the sediment redox potential and nutrient concentrations in the interstitial waters were similar to those observed in situ in the lagoon
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