@article{osburn_handsel_peierls_paerl_2016, title={Predicting Sources of Dissolved Organic Nitrogen to an Estuary from an Agro-Urban Coastal Watershed}, volume={50}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/acs.est.6b00053}, DOI={10.1021/acs.est.6b00053}, abstractNote={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.}, number={16}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Osburn, Christopher L. and Handsel, Lauren T. and Peierls, Benjamin L. and Paerl, Hans W.}, year={2016}, month={Jul}, pages={8473–8484} }
 @article{brym_paerl_montgomery_handsel_ziervogel_osburn_2014, title={Optical and chemical characterization of base-extracted particulate organic matter in coastal marine environments}, volume={162}, ISSN={["1872-7581"]}, DOI={10.1016/j.marchem.2014.03.006}, abstractNote={Absorbance and fluorescence measurements were measured on base-extracted particulate organic matter (BEPOM) to examine POM biogeochemistry in coastal marine environments. BEPOM trends from August 2011–September 2012 in the Neuse River Estuary (NRE) were compared against single sampling events in Charleston Harbor (CHS) and the inner Louisiana–Texas Shelf of the Gulf of Mexico (GOM) in July 2011 and July 2012, respectively. Spectral slope values, S275–295, and the ratio of spectral slopes, SR values, were mainly influenced by distinct structure in the UV-B region of BEPOM absorption spectra, which was similar to prior laboratory work on autochthonous, planktonic sources of chromophoric dissolved organic matter (CDOM). A PARAFAC model with five components was fit to BEPOM excitation–emission matrix (EEM) fluorescence data. Excitation and emission spectra of the five components were similar to those found for dissolved organic matter (DOM) in other coastal environments, with two components attributed to planktonic sources and two components attributed to terrestrial (humic) sources. A fifth component was attributed to microbial humic substances. Principle components analysis of PARAFAC results separated autochthonous, planktonic components from allochthonous, terrestrial components and explained > 70% of the variance in the data. Surface water stable carbon isotope (δ13C) values of BEPOM from the NRE and CHS ranged from − 29 to − 23‰, with most enriched values occurring synchronous with high Chl-a concentrations, and indicating that enriched δ13C values in BEPOM reflected a planktonic source. Notably, δ13C-BEPOM values for the GOM shelf below 50 m water depth were depleted (<− 30‰), and a mixing model indicated that 30–40% of the POM could originate from methanic carbon. BEPOM absorption and fluorescence results suggested a planktonic POM as a source of CDOM in coastal marine environments.}, journal={MARINE CHEMISTRY}, publisher={Elsevier BV}, author={Brym, Adeline and Paerl, Hans W. and Montgomery, Michael T. and Handsel, Lauren T. and Ziervogel, Kai and Osburn, Christopher L.}, year={2014}, month={May}, pages={96–113} }
 @article{osburn_handsel_mikan_paerl_montgomery_2012, title={Fluorescence Tracking of Dissolved and Particulate Organic Matter Quality in a River-Dominated Estuary}, volume={46}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es3007723}, DOI={10.1021/es3007723}, abstractNote={Excitation-emission matrix (EEM) fluorescence was combined with parallel factor analysis (PARAFAC) to model base-extracted particulate (POM) and dissolved (DOM) organic matter quality in the Neuse River Estuary (NRE), North Carolina, before and after passage of Hurricane Irene in August 2011. Principle components analysis was used to determine that four of the PARAFAC components (C1-C3 and C6) were terrestrial sources to the NRE. One component (C4), prevalent in DOM of nutrient-impacted streams and estuaries and produced in phytoplankton cultures, was enriched in the POM and in surface sediment pore water DOM. One component (C5) was related to recent autochthonous production. Photoexposure of unfiltered Neuse River water caused an increase in slope ratio values (S(R)) which corresponded to an increase in the ratio C2:C3 for DOM, and the production of C4 fluorescence in both POM and DOM. Changes to the relative abundance of C4 in POM and DOM indicated that advection of pore water DOM from surface sediments into overlying waters could increase the autochthonous quality of DOM in shallow microtidal estuaries. Modeling POM and DOM simultaneously with PARAFAC is an informative technique that is applicable to assessments of estuarine water quality.}, number={16}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Osburn, Christopher L. and Handsel, Lauren T. and Mikan, Molly P. and Paerl, Hans W. and Montgomery, Michael T.}, year={2012}, month={Jul}, pages={8628–8636} }