Influence of environmental factors on N2O emissions from denitrification in streambed sediments of low-relief coastal streams

N₂O production and consumption within sediments of gaining, low-relief coastal streams proximal to agricultural fields was examined in the context of how changes in temperature, NO₃^- loading, and pore water velocity can affect the concentration of N₂O in the groundwater and efflux of N₂O from the sediment. Sediment cores extracted from streams on the Eastern Shore of Virginia were used as vertical-flow columns and operated under conditions that varied, in turn, each of the aforementioned parameters systematically, resulting in 36 scenarios. Water samples were extracted after equilibration in each scenario from ports in the columns and were analyzed for major anions, dissolved O₂, and N₂O. Results showed a complex interaction of parameters affected the production and consumption of N₂O. As temperature increased from 5° to 15° C, N₂O fluxes increased an order of magnitude, from a maximum of 265 to 2949 μg N m^-2 h^-1. Increasing pore water velocity (0.5 to 4.5 cm h^-1) resulted in a generally increasing trend in the N₂O flux at 5° C while fluxes tended to decrease with increasing flow at 15° C. In addition, increasing NO₃^- loading (5 to 15 to 25 mg L^-1 NO₃^--N) was not accompanied by a concomitant increase or decrease in N₂O production. The median N₂O flux from all scenarios was 29.64 μg N m^-2 h^-1. Results from this work indicate that there is a significant temperature effect on N₂O fluxes from stream bed sediments which needs to be accounted for in estimates of N₂O emissions in a changing climate. In addition, more work is planned in order to increase the understanding of how NO₃^- loading affects N₂O fluxes from stream bed sediments.