Fluorescence spectral characteristics of sediments dissolved organic matter in the Qinjiang River estuary，Beibu Gulf

Dissolved organic matter (DOM) is an organic mixture with a highly complex chemical composition and structure. It plays a pivotal role in regulating the chemical forms of trace elements in aquatic environments, as well as in the migration and transformation of pollutants, making it critically important for environmental pollution evaluation and remediation. This study aims to explore the composition, structure, and sources of DOM in the sediments of the Qinjiang Estuary in the Beibu Gulf. The material composition and source characteristics of DOM in the sediments from the Qinjiang Estuary were analyzed in depth using ultraviolet-visible spectroscopy (UV-Vis), three-dimensional fluorescence spectroscopy (3D-EEMs), and parallel factor analysis (PARAFAC). The results indicate that the primary components of DOM in the Qinjiang Estuary sediments are humic substances and protein-like (or tannin-like) compounds. These DOM components are influenced by both internal and external sources, exhibiting weak humic characteristics and strong biological activity. Moreover, the three types of humic-like substances and protein-like (or tannin-like) compounds in the DOM may originate from the same source. In general, DOM in the Qinjiang Estuary sediments is more significantly affected by external inputs, suggesting the need to strengthen the control and management of external pollutant inputs. This study not only contributes to a comprehensive understanding of the characteristics of DOM in the sediments of the Qinjiang estuary in Beibu Gulf but also provides a new perspective on the biogeochemical processes of DOM in estuarine sediments, offering a scientific basis for sediment pollution prevention and environmental management in the Qinjiang estuary area.