title: Predicting Sources of Dissolved Organic Nitrogen to an Estuary from an Agro-Urban Coastal Watershed.
abstract: Dissolved organic nitrogen (DON) is the nitrogen (N)-containing component of dissolved organic matter (DOM) and in aquatic ecosystems is part of the biologically reactive nitrogen pool that can degrade water quality in N-sensitive waters. Unlike inorganic N (nitrate and ammonium) DON is comprised of many different molecules of variable reactivity. Few methods exist to track the sources of DON in watersheds. In this study, DOM excitation-emission matrix (EEM) fluorescence of eight discrete DON sources was measured and modeled with parallel factor analysis (PARAFAC) and the resulting model ("FluorMod") was fit to 516 EEMs measured in surface waters from the main stem of the Neuse River and its tributaries, located in eastern North Carolina. PARAFAC components were positively correlated to DON concentration. Principle components analysis (PCA) was used to confirm separation of the eight sources and model validation was achieved by measurement of source samples not included in the model development with an error of <10%. Application of FluorMod to surface waters of streams within the Neuse River Basin showed that while >70% of DON was attributed to natural sources, nonpoint sources, such as soil and poultry litter leachates and street runoff, accounted for the remaining 30%. This result was consistent with changes in land use from urbanized Raleigh metropolitan area to the largely agricultural Southeastern coastal plain. Overall, the predicted fraction of nonpoint DON sources was consistent with previous reports of increased organic N inputs in this river basin, which are suspected of impacting the water quality of its estuary.
authors.affiliation: Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University , Raleigh, North Carolina 27695 United States.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Osburn
authors.affiliation: Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University , Raleigh, North Carolina 27695 United States.
authors.forename: Lauren T
authors.initials: LT
authors.lastname: Handsel
authors.affiliation: Institute of Marine Sciences, University of North Carolina at Chapel Hill , Morehead City, North Carolina 28557 United States.
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Peierls
authors.affiliation: Institute of Marine Sciences, University of North Carolina at Chapel Hill , Morehead City, North Carolina 28557 United States.
authors.forename: Hans W
authors.initials: HW
authors.lastname: Paerl
mesh_terms: D000383:Agriculture; D017753:Ecosystem; D063366:Estuaries; D009584:Nitrogen / Q000032:analysis*; D045483:Rivers; D060753:Water Quality
chemical_list: D009584:Nitrogen