作者：Xu, R., Du, Y., Wu, T., et al.

As the largest reactive organic carbon pool, dissolved organic matter (DOM) plays a crucial role in various biogeochemical processes within lake ecosystems. Thus, examining the chemical composition of lake DOM and its variations is vital for the protection of lake water environments. Research on the temporal and spatial variability of DOM in specific large lakes remains limited. This study focuses on Dongting Lake, located in the central Yangtze River area, as a representative case, with an emphasis on investigating the spatiotemporal variability of DOM and its controlling factors. The main methods employed include 3D excitation-emission matrix fluorescence spectroscopy (3D-EEMs) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results showed that endogenous DOM, characterized by an increase in saturated compounds and aliphatics, was more abundant during the dry season. While in the wet season, terrestrial DOM was relatively more abundant, exhibiting higher aromaticity, humification, and recalcitrance. This shift was mainly attributed to hydrologic-induced expansion in the lake area, which facilitated the input of terrestrial DOM into the lake. Anthropogenic activities, including agricultural off and urban wastewater discharge, also influenced DOM composition, evidenced by higher proportions of CHON and polyphenolic compounds, and O3S + O5S compounds in the lake areas surrounded by corresponding land use types. DOM underwent photo-degradation into small molecular compounds during transport, accumulating in Eastern Dongting Lake area under the impounding effect of the Yangtze River, and underwent transformation due to microbial activity at the sediment-water interface. This study improves our understanding of DOM dynamics in large lakes and provides a scientific basis for the sustainable development and management of water resources and wetland ecological protection in Dongting Lake.

（来源：Journal of Hydrology 2025   DOI: 10.1016/j.jhydrol.2025.133831）