Nitrate recycling versus removal in the Cape Fear River estuary

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Taylor B. Graham (Creator)
The University of North Carolina Wilmington (UNCW )
Web Site:
Steve Ross

Abstract: The Cape Fear River Estuary (CFRE) drains the largest watershed in North Carolina. Anthropogenic inputs of nutrients to this estuary have increased due to the rise in population and subsequent demand for agricultural products in southeastern North Carolina. Dissolved inorganic nitrogen (DIN) enters from tributaries, wet deposition, groundwater and wastewater runoff. Typical of many estuarine systems in the southeastern United States, increased nitrogen loading is coincident with upstream salinity encroachment resulting from fresh drinking water withdrawals and sea level rise. Nitrate is the dominant form of DIN in oxidized waters and was the primary area of focus for this study. Benthic nitrate recycling (DNRA) and removal (ANAMMOX and denitrification) mechanisms were studied in the CFRE, North Carolina. A rapid and real time method using a 15N tracer was developed to simultaneously quantify rates of denitrification, anaerobic ammonium oxidation (ANAMMOX) and dissimilatory nitrate reduction to ammonium (DNRA) in a single sediment sample. Rates were assessed along the estuarine axis seasonally, as the salinity front migrated up and downstream. The ANAMMOX and denitrification rates were generally highest upstream at lower salinities, whereas the DNRA rates were always highest at elevated salinities. A strong, positive correlation was found between ANAMMOX and denitrification rates. A combined approach of laboratory measurements with fresh and transplanted sediment incubations were done in conjunction with geochemical monitoring of porewaters. Rates of ANAMMOX and denitrification tended to be highest when sulfide concentrations were lowest (upstream). Conversely, DNRA was highest when sulfide concentrations were elevated (downstream).

Additional Information

A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Nitrogen cycle--North Carolina--Cape Fear River Estuary, Water--Nitrogen content--North Carolina--Cape Fear River Estuary, Nitrates--Environmental aspects--North Carolina--Cape Fear River Estuary
Nitrates -- Environmental aspects -- North Carolina -- Cape Fear River Estuary
Water -- Nitrogen content -- North Carolina -- Cape Fear River Estuary
Nitrogen cycle -- North Carolina -- Cape Fear River Estuary

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