Spectral Characteristics of Dissolved Organic Matter in Sediments from Yuanhe River Basin

Abstract

Dissolved organic matter （DOM） plays an important role in indicating the pollution of the water environment, and sediment is the main source of endogenous pollution of the water environment. Research on the spectral characteristics of DOM in sediments was important for the interpretation of water environment pollution. In this study, UV-visible absorption spectroscopy and three-dimensional fluorescence spectroscopy combined with the parallel factor analysis （PARAFAC） were used to analyze the fluorescent components, sources, and influencing factors of DOM in sediments from the Yuanhe River Basin. The results showed that the average of ω（TN）, ω（TP）, and ω（OM） in sediments from the Yuanhe River Basin were 0.52, 0.66, and 21.22 g·kg-1, respectively. The concentrations of total nitrogen and total phosphorus increased along the flow direction. In addition, the sediment DOM from the Yuanhe River Basin mainly originated from terrestrial sources. The chromophoric DOM concentration and aromaticity of DOM from the downstream reaches were significantly higher than those from the upstream and midstream reaches. Based on PARAFAC, four fluorescent components of DOM in sediments from the Yuanhe River Basin were identified, including three humus-like components （C1, C3, and C4） and one protein-like component （C2）. The sediment DOM was dominated by humus-like materials. Moreover, the fluorescent intensity of the fluorescent components was higher in the downstream reaches. Redundancy analysis revealed that the physicochemical properties of sediments in the mainstream and downstream reaches played a more significant role in the spectral properties of DOM. Phosphorus pollution and the terrestrial humus-like substance of sediment DOM were homologous. These results indicated that the spectral properties of DOM were the indicator of water environmental pollution in the region with strong anthropogenic influence.