Science Serving Maryland's Coasts

Nicholas Dylla, Elmhurst College

Class Year: 

Project Title: 

A Potent Greenhouse Gas Source: Nitrous Oxide Emission during Base Flow and Storm Flow in the Choptank River Basin


Nitrous Oxide (N2O) is a potent greenhouse gas, and streams, rivers, and groundwater act as sources of N2O to the atmosphere. Four streams were sampled in four agriculturally dominated watersheds in the Choptank River Basin. N2O gas concentrations and stream parameters were measured to estimate N2O flux to the atmosphere for comparison with N2O fluxes estimated with the IPCC protocols. N2O fluxes (F, μmol N2O - N m-2 h-1) were calculated using measured N2O-N concentrations (Cm, μmol N2O-N L-1) in excess of atmospheric equilibrium (Ceq, μmol N2O-N L-1) and a gas exchange coefficient k (m h-1) (F = (Cm - Ceq) * k). Fluxes of N2O ranged over 0.49-190.69 N2O-N m-2 h-1 in the four watersheds, and were similar to those calculated using the IPCC protocols and also to N2O 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—N2O levels decreased during the storm event, while DO levels increased—which suggests that the rainfall itself caused an increase in gas exchange.