Overall, denitrification represented a sink of approximately 30% of the daily N loading transported in middle summer, highlighting a previously underestimated role of the Po River Delta. Denitrification was stimulated by both NO 3 − availability in the Po River water and organic enrichment of sediment likely determined by salinity-induced flocculation of particulate organic load, and inhibited by increasing salinity, along the river–sea gradient. The correlation between NO 3 − consumption and N 2 production rates demonstrated that denitrification was the main process responsible for reactive N removal. Benthic fluxes of dissolved inorganic nitrogen (N) and denitrification rates were measured in laboratory incubations of intact sediment cores collected, along a salinity gradient, at three sections of the Po di Goro, the southernmost arm of the Po Delta. The aim of the present study was to quantify the contribution of denitrification in attenuating the NO 3 − loading transported to the sea during summer. However, benthic N dynamics and the relevance of denitrification in its delta have not yet been described. The Po River (Northern Italy) is a worldwide hotspot of eutrophication.
In transitional environments, the role of sediments biogeochemistry and denitrification is crucial for establishing their buffer potential against nitrate (NO 3 −) pollution.
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