2009 BES Annual Meeting Presentation and Poster Abstracts
SOURCES AND TRANSFORMATIONS OF NITROGEN, CARBON, AND PHOSPHORUS IN THE POTOMAC RIVER ESTUARY
Co-Authors: Michael J. Pennino, Sujay Kaushal, and Sudhir Murthy
Abstract: Global transport of nitrogen (N), carbon (C), and phosphorus (P) in river ecosystems has been dramatically altered by urbanization. We examined the capacity of the Potomac River, a major tributary of the Chesapeake Bay, to transform carbon, nitrogen, and phosphorus inputs from the world’s largest advanced wastewater treatment facility (Washington D.C. Water and Sewer Authority). Effluent samples and surface water from the Potomac River were analyzed for dissolved and particulate carbon, nitrogen, and phosphorus. Sources of organic matter were characterized using fluorescence spectroscopy, excitation emission matrices (EEMs), and PARAFAC modeling. Sources of nitrate were tracked using stable isotopes of nitrogen and oxygen. Stoichiometric ratios of C, N, and P were determined along the River and related to changes in flow conditions. Long-term records of effluent inputs and downstream C, N, and P levels were compared to assess historical transformations. Land use and historical water chemistry data were also compared to determine the relative importance of nonpoint versus point sources of nutrients. Preliminary data from EEMs suggest more humic-like organic matter is found above the wastewater treatment plant, while protein-like organic matter is present below the treatment plant. Levels of N and P increase within the vicinity of the wastewater treatment outfall, but decrease rapidly downstream, potentially indicating uptake and transformation. C/N ratios increase downstream, but C/P ratios have no corresponding trend. Greater knowledge of sources and transformations of C, N, and P will be important in predicting changes in the amounts, forms, and stoichiometry of nutrient loads to coastal waters.