The spectral characterization on chromophoric dissolved organic matter released from leaching of wetland plant litter in Poyang Lake under inundation

Chromophoric dissolved organic matter (CDOM) leached from litter plays a key role in wetland biogeochemical cycling. However, the release patterns and driving mechanisms of CDOM from large lake wetland plant litter under inundation remain poorly understood. This study investigated litter from three dominant plants (Carex cinerascens, Triarrhena lutarioriparia, Phragmites australis) in the Poyang Lake wetland. Simulated inundation experiments combined with excitation–emission matrix fluorescence spectroscopy and parallel factor analysis (PARAFAC) were used to examine the leaching dynamics and compositional evolution of litter-derived CDOM. The results showed that CDOM concentration and humification degree increased with inundation duration, while both CDOM and dissolved organic carbon (DOC) were released rapidly during the first 10 days. CDOM content and composition differed among plant types and components, with leaf litter releasing higher DOC, CDOM and fluorescence intensity than stem litter. CDOM from Phragmites australis leaves showed the lowest degradation over the 25-day inundation period. PARAFAC identified three humic-like and two protein-like fluorescent components. The humic-like C1 component, characterised by high aromaticity and large molecular weight, exhibited low degradability. Protein-like components dominated the early stage of inundation, whereas humic-like substances gradually became dominant. These findings improve understanding of litter-derived CDOM dynamics and biogeochemical processes in floodplain lake wetlands.