Fluorescence characteristics of dissolved organic matter in relation to land use in the wetland waters of Poyang Lake, China

Dissolved organic matter (DOM) plays a fundamental role in regulating carbon cycling and mediating various biogeochemical processes in wetland ecosystems. In this study, DOM absorption, fluorescence spectra, and other data from 30 representative sites of wetland waters in Poyang Lake were collected in 2021. The composition, spatial distribution, and source characteristics of DOM were analyzed by three-dimensional (3D) fluorescence spectroscopy technique combined with parallel factor analysis (PARAFAC). The findings showed that (1) 2 humic-like constituents (C1, C2) and a tryptophan constituent (C3) were recognized in the PARAFAC model; (2) the fluorescent DOM (FDOM) constituents in the Poyang Lake wetlands showed spatial differences, with the fluorescence intensity of C1 and C2 higher in the south and north sections and lower in the east and west sections, and the fluorescence intensity of C3 in the northern wetland waters higher than other areas; (3) DOM in the Poyang Lake wetlands was predominantly influenced by inputs from terrestrial sources. Land use type analysis showed that marshland and cultivated land have a great impact on DOM in Poyang Lake, and spatial differences of fluorescent components showed the impacts of human-induced land use variations. The results enhance our understanding of the significant role of land use in biogeochemical processes, particularly in the export of DOM to aquatic environments. Furthermore, they provide guidance for the management and protection of water resources in the Poyang Lake wetland.