Dissolved and particulate organic matter fluorescence in coastal river systems in relation to land use and carbon transfer

Recently, dissolved organic matter (DOM) fluorescence has been employed in river systems to understand carbon cycling, land use, and to some degree climate change. Excitation-emission matrices (EEMs) of DOM fluorescence spectra can be modeled using multivariate statistical approaches (e.g., parallel factor analysis, PARAFAC) to elucidate discrete and subtle changes to DOM properties. These changes are then often related to watershed properties (e.g., land use-land cover), hydrology, etc. This talk will build on that body of work, but also introduce the EEM-PARAFAC technique for water- and base-extractable OM (WEOM and BEOM, respectively) from particles in the Neuse River, eastern North Carolina, a coastal river which is under stress from land use (urbanization and agriculture) and climatic changes (periods of drought and increasing frequency and intensity of tropical storms) occurring in its watershed. POM fluorescence EEMs will be discussed in tandem with corresponding DOM fluorescence EEMs in several tributaries of the Neuse River, in addition to the Neuse Proper. The fluorescence data will be interpreted in the context of stream discharge, particle concentrations, and dissolved organic carbon (DOC) concentrations. Results from experiments and PARAFAC models showing the similarities and differences between WEOM, BEOM, and DOM fluorescence properties illuminate distinct relationships between POM and DOM cycling, and carbon transfer between these organic matter pools. The overall aim of this talk is to introduce the combined WEOM+BEOM+DOM fluorescence approach as a way to model organic matter in river systems through data fusion of these three fluorescence signatures.