Compositional and structural characteristics of dissolved organic matter in overlying water of the Chaobai River and its environment significance.

The composition and structure of dissolved organic matter (DOM) play vital roles in the material cycle of river ecosystems. Based on ultraviolet-visible absorption spectroscopy, excitation-emission matrix fluorescence spectroscopy, and ultrahigh-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry technology, this study comprehensively characterized the composition and structure of DOM in the overlying water of the Chaobai River in order to determine the potential environmental impact of DOM on the water quality. The results showed that the DOM content of the overlying water in the Chaobai River was between 10.94 and 28.13 mg/L. The main DOM component of the overlying water was humus (70.94%). The relative abundance of CHOS compounds in the Chaobai River was lower than Maozhou River (urbanized river) and significantly higher than Xiangxi Bay (suburban river). In addition, the DOM composition and structure of the overlying water were closely related to anthropogenic input, microbial activity, and phytoplankton. In particular, chlorophyll a can indirectly reflect fresh autochthonous DOM content and composition in the overlying water. The results of this study further reveal the characteristics of suburban rivers and provide theoretical basis and guidance for the water quality evaluation and pollution control of the Chaobai River and other suburban rivers worldwide.