Assessing the dynamics of chromophoric dissolved organic matter (CDOM) in the Yellow Sea and the East China Sea in autumn by EEMs-PARAFAC

Abstract

In this study we have successfully characterized the fluorescent components of chromophoric dissolved organic matter (CDOM) in the Yellow Sea and the East China Sea in autumn using excitation-emission matrix fluorescence spectroscopy (EEMs) combined with parallel factor analysis (PARAFAC). PARAFAC aids the characterization of fluorescence CDOM by decomposing the fluorescence matrices into individual components. Four humic-like components (C1, C2, C3, and C4), one marine biological production component (C6), and two protein-like components (C5 and C7) were identified by PARAFAC. We researched the distributional patterns of fluorescence intensity, regression analyses between salinity, chlorophyll a concentration and fluorescence intensities of individual fluorophore, and regression analysis between salinity and fluorescence intensities percent of individual fluorophore. The results revealed that C2 and C4 showed conservative mixing behavior, while C1 and C3 possessed conservative mixing behavior in high salinity region and additional behavior in low and middle salinity region, which were considered to be derived from riverine and degradation of organic matter from resuspended and/or sinking particles and show non-conservative mixing behavior. In addition to riverine sources, the tryptophan-like C5 may receive widespread addition (likely from photo-degradation or biodegradation), while the most likely sources for the one marine humic-like C6 and tyrosine-like C7 were biological activity and microbial processing of plankton-derived CDOM, which were suggested to be of autochthonous origin and biologically labile. The application of EEM-PARAFAC modeling presents a unique opportunity to observe compositional changes, different mixing behavior and temporal variability in CDOM in the Yellow Sea and the East China Sea.