Production and release of N²O from the Potomac Estuary 1

Measurements of dissolved O 2 , N 2 O, NH 4 + , NO 2 − , and NO 3 − are used to study the biogeochemistry of nitrogen in the Potomac River near Washington, D.C. The nutrient budget of the Potomac is dominated by sewage inputs from treatment plants at Blue Plains and Alexandria. Measurements taken in July and September 1977 indicate large supersaturated concentrations of N 2 O and exhibit significant short‐period variations over distances >40 km. Concentrations of N 2 O and O 2 appear to be inversely correlated and there are indications that N 2 O may be produced primarily near the sediment‐water interface. Nitrous oxide is released to the air on a time scale of about 1 day and gas exchange may occur mainly in shallow embayments in response to turbulence associated with tidal currents. Release of N 2 O to the atmosphere takes place at a rate of about 10 3 kg·d −1 and may be attributed to prompt conversion to N 2 O of between 1 and 5% of the total nitrogen input.