[Spectral Characteristics and Sources of Dissolved Organic Matter With Different Relative Molecular Weight from Rainwater From Summer and Autumn in the Zhoucun Reservoir Based on UV-Vis and EEMs].

Based on excitation emission matrix spectroscopy (EEMs) technology combined with parallel factor analysis (PARAFAC) and UV-Vis spectra, we analyzed the spectral characteristics and sources of dissolved organic matter (DOM) in rainwater with different DOC molecular weight in summer and autumn in the Zhoucun Reservoir. The results show that the UV-Vis absorption spectrum of DOM have no notably characteristic peak and the variation coefficient of the absorption coefficient ranges between 75% and 469%, which shows the properties of DOM with different molecular weight. The changes of and E3/E4 show that the relative concentration of DOM and the proportion of fulvic acid in DOM both increase from summer to autumn, respectively; Two humic-like substances (C1, C2), one fulvic-like substance (C3), and one protein-like substance (C4) were identified with the PARAFAC model, with a significant correlation coefficient (<0.01) in C1&C2/C3/C4 and C2&C3, respectively. The total DOM fluorescence intensity and the fluorescence intensity of each component exhibit significantly different distributions (<0.01). Moreover, C1+C2 account for the majority proportion of DOM and C3 and C4 exhibit an increase and decrease from summer to autumn, respectively. The rainwater in summer and autumn both exhibita strong autochthonous component characteristics and the summer rainwater has higher autochthonous characteristics. The PCA shows that the spectral characteristics of the rainwater exhibit notable differences. Moreover, C1, C2, and C3 exhibit a significant correlation coefficient (<0.01) with DOM indices[HIX, Fn(355), Fn(280), E3/E4, ] and water quality parameters. The results contribute to the future exploration and control of organic carbon pollution sources by managers of the Zhoucun Reservoir.