Deliverable I3d3 Rapporto tecnico - Ciclo dei nutrienti e stato ecologico buono: proposta di nuove misure basate sulle caratteristiche di habitat e idromorfologiche locali degli ambienti acquatici e possibilità di up-scaling

Despite the enormous efforts made in recent years to face the problems relating to the alteration of nutrient cycles, both in scientific and management terms, we are still far from effective resolutions and fluxes of nitrogen (N) and phosphorus (P) through river basins continue to be very high. In Europe, the achievement of good ecological status, required by the WFD before 2015, necessitates rapid uptake of effective and verifiable measures to reduce nutrient loading to surface waters and groundwater. Over the last decade there has been increasing evidence that biogeochemical processes occurring naturally in portions of the river ecosystem (buffer strips) and / or in the riverbed where are able to modulate the concentrations of nutrients exported downstream. For these reasons, within INHABIT project, we performed an investigation aimed to deepen the knowledge of the factors controlling the transformations of nutrients in river systems, with particular attention to the hydro-morphological features and habitats. Some nutrient retention metrics have been estimated through experiments of nutrient additions in some selected river sites in Sardinia and Piedmont (Italy).The results highlight the importance of the areas of "transient storage" (As) in regulating the efficiency of NH4 and PO4 retention, expressed by the values of "uptake length" in both regions. Moreover we observed a highly significant relationship between As (normalized for the river section) and the ratio between the width and the depth (w/d) of the channel, after having separated the river stretches in natural and resectioned channels.