Evaluating CDOM Sources Using Excitation-Emission Matrix Fluorescence and Parallel Factor Analysis, and their Links to Water Quality in Highly Polluted Rivers in China

Chromophoric dissolved organic matter (CDOM) is a valuable optically active substance. This study examined the seasonal characteristics of fluorescent CDOM components in the Yinma and Songhua rivers, highly polluted watershed tributaries of the Songhua River, and a drinking water source for the city of Changchun, China. Parallel factor analysis (PARAFAC) and excitation-emission matrix (EEM) spectra were used to assess CDOM fluorescence. Four components attributed to CDOM in 51 water samples were identified: three were humic-like (C1, C3, and C4) and one was protein-like (C2). The average fluorescence intensities of the four components showed seasonal variation from May to November 2016. A positive linear correlation was found between components C3 and C4 (R = 0.86, p<0.001). The results from this investigation demonstrated that the frequency of rainfall and human activities may be the main factors influencing the quantity and quality of CDOM in samples collected from the watershed, and that the Yinma and Yitong rivers were polluted by terrestrial and agricultural pollution. Furthermore, the utility of combining EEM fluorescence and PARAFAC to study CDOM dynamics for different seasons and to quantify CDOM components for similar environmental (water quality) conditions was established.