Student Research Presentations
A potent greenhouse gas source: nitrous oxide emission during base flow and storm flow in the Choptank River basin
ASLO Aquatic Sciences Meeting, Granada, Spain
Nitrous Oxide (N20) is a potent greenhouse gas, and streams, rivers, and groundwater act as sources of N20 to the atmosphere. Four streams were sampled in four agriculturally dominated watersheds in the Choptank River Basin. N20 gas concentrations and stream parameters were measured to estimate N20 flux to the atmosphere for comparison with N20 fluxes estimated with the IPCC protocols. N20 fluxes (F, µmol N20-N m-2 h-1) were calculated using measured N20-N concentrations (Cm, µmol N20-N L-1) in excess of atmospheric equilibrium (Ceq, µmol N20-N L-1) and a gas exchange coefficient k (m h-1) (F = (Cm - Ceq) * k). Fluxes of N20 ranged over 0.17-23.10 µmol N20-N m-2 h-1 in the four watersheds, and were similar to those calculated using the IPCC protocols and also to N20 fluxes from nearby agricultural fields. The IPCC flux estimates were not statistically different from the empirically derived fluxes (p > 0.05). This approach can potentially provide a quick method to estimate the role of gas fluxes from streams in watersheds. Also, sampling occurred during a storm event—N20 levels decreased during the storm event, while DO levels increased—which suggests that the rainfall itself caused an increase in gas exchange.