Advances in understanding the contributions of microbial dissolved organic matter to the fluorescence signature of natural waters using parallel factor analysis

Dissolved organic matter (DOM) is present in all aquatic ecosystems and plays and important role in the global carbon cycle. DOM can be characterized using fluorescence spectroscopy. The measurements that are collected from a DOM fluorescence scan are commonly referred to as three dimensional excitation-emission matrices (EEMs) (Coble et al, 1990; McKnight et al 2001). In this study EEMs were run through an already established model (Cory and McKnight), but we were left with areas of high residuals, e.g. areas of the EEM that were not modeled as well as one would like. Therefore, these results identified the need for the creation of a new model; one specialized towards fluorescence data for DOM enriched in microbial products. The new model used samples taken from 3 low humic sites and 2 microbial incubations. Using parallel factor analysis (PARAFAC) a 5-component model was validated, with component C1 being the microbial input.