@ 1978, by the American Society of Limnology and Oceanography, Inc. Production and release of N20 from the Potomac Estuary1

Measurements of dissolved 02, NzO, NH4+, NOz-, and NOs- are used to study the biogeo-chemistry 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 Alex-andria. Measurements taken in July and September 1977 indicate large supersaturated con-centrations of NzO and exhibit significant short-period variations over distances>40 km. Concentrations of N20 and O2 appear to be inversely correlated and there are indications that N,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 embaymcnts in response to turbulence associated with tidal currents. Release of N20 to the atmosphere takes place at a rate of about 10 ’ kg * d- ’ and may be attributed to prompt con-version to N,O of between 1 and 5 % of the total nitrogen input. We report here results from an experi-mental study designed to quantify some aspects of the nitrogen cycle in the Po