Spectral Characteristics and Sources of Dissolved Organic Matter from Landscape River During Flood Season in Suzhou Based on EEMs and UV-vis

Abstract

Based on excitation emission matrix spectroscopy (EEMs) technology combined with the parallel factor analysis (PARAFAC) and UV-vis spectra, the spectral characteristics and sources of dissolved organic matter (DOM) from a landscape river were analyzed during different periods of the flood season in Suzou. Four fluorescent components were identified using the PARAFAC model, including two humus-like components (C1, C4) and two protein-like components (C2, C3), with a significant correlation coefficient (P<0.01) in C2 and C3/C4 and C3 and C4, respectively. During the early flood season, the total fluorescence intensity of the DOM in the river was relatively higher due to the influence of initial rainwater but reduced significantly towards the middle and late flood season. The fluorescence characteristic parameters indicated that the autochthonous contribution of DOM were substantial during the early stages of the flood season. On the contrary, there were increased levels of DOM largely from terrestrial origins during the middle flooding period. During the entire flood season, SUVA254, SUVA260, and E2/E3 exhibited the same trend, that is, decreasing first and then increasing. As a result of the continuous heavy rainfall during the flood season, the nitrogen and phosphorus nutrient content in the channel increased. The algae population did not proliferate in large quantities because of the strong hydrodynamic conditions experienced throughout the flood season. The fluorescence components C2, C3, and C4 exhibited a significant correlation coefficient (P<0.01) with the characteristic parameters (FI, HIX, BIX, and β:α). All the fluorescence components had a high correlation (P<0.05) with DOC. There was a considerable correlation between fluorescence component C1 and Chla. The principal component analysis revealed that the DOM components in the landscape river during different periods of the flood season exhibited notable differences, and the continuous heavy rainfall during the flood season has a substantial influence on the content of C2, C3, and C4 components in the water body.