Spatial variability of denitrification in tidal freshwater rivers

Denitrification (DNF) rates in river channel sediments are thought to be lower than the riparian zone, but few studies have examined spatial variability of DNF in the tidal freshwater zone (TFZ). DNF was measured in the channel, bank, and floodplain at upstream and downstream sites of two TFZs of rivers in Eastern NC with different nitrate regimes, the New River and Newport River, using membrane inlet mass spectrometry. DNF was usually similar between sites regardless of inundation regime. The contribution of channel sediments to the net N2 flux was greater than the riparian zone in the New River, and less in the Newport River. Sediment oxygen demand was usually correlated to DNF in the New River, and periodically in the Newport River. These data provide new information on the relative importance of the channel, bank, and floodplain to TFZ DNF and will improve estimates of N removal by the TFZ