Nitrification and Uptake as drivers of seasonal δ18O and δ15N variation of nitrate
Résumé
Nitrogen loads in the Scheldt Estuary (Belgium – The Netherlands) decreased since the early 2000s following enhanced wastewater treatment. However, nitrate concentrations have generally increased as a result of increased nitrification and decreased denitrification due to improved oxygen conditions while diffuse nitrate inputs from agriculture did not change. Nitrate concentrations vary strongly on a seasonal basis, with lowest concentrations observed in summer and highest in winter. We aimed at identifying the internal nitrate sinks and sources in the freshwater to oligohaline parts of the estuary in order to understand the fate of nitrate in the highly eutrophic Scheldt system.