Characterizing natural organic material from the Occoquan Watershed (Northern Virginia, US) using fluorescence spectroscopy and PARAFAC.

Surface water samples from the Occoquan Watershed (Virginia, US) were collected during summer baseflow conditions and characterized by excitation-emission matrix (EEM) fluorescence spectroscopy and parallel factor analysis (PARAFAC). Based on 55 samples, PARAFAC identified three individual fluorophore moieties, which were attributed to humic-like, fulvic-like, and protein-like materials. The categorization of these seemingly universal fluorophore moieties in aqueous systems was consistent with expected analyte concentrations that were independently measured by traditional wet chemistry techniques. The relative distribution of the three fluorophore fractions varied among the different land use catchments, especially in locations of known anthropogenic activity. Distinctive relationships between the fulvic-like and protein-like materials were observed for catchments known to be influenced by anthropogenic activity and those believed to reflect more natural environments, suggesting that this technique could be used to monitor human impact on aquatic systems. Finally, PARAFAC can be used to provide estimates (+/-30%) of select analyte concentrations in surface water. The results of this study support the use of EEM and PARAFAC analyses by watershed managers and other personnel interested in understanding organic matter behavior in aquatic systems.