Deciphering Labile and Refractory Organic Components in Natural Waters: Implications for Lake Carbon Cycling

Photo-incubation and bio-incubation are key processes regulating the chemical composition and fate of dissolved organic matter (DOM) in inland surface waters. However, the reactivity and transformation mechanisms of different DOM components in inland natural waters remain inadequately characterized. In this study, three representative inland water bodies, an alpine lake dominated by phytoplankton, a macrophyte-dominated lake, and an urban river, were investigated using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) coupled with optical spectroscopy. Potential chemical reaction predictions were combined to elucidate the molecular transformation mechanism of DOM in photochemical and microbial incubation processes. Our results demonstrate that the critical role of intrinsic molecular properties of DOM, notably molecular weight, unsaturation, and humification degree, in regulating its reactivity and driving compositional shifts during biogeochemical processes. Molecular weight determined bio-incubation activity, while source-specific highly unsaturated and phenolic compounds modulated lacustrine DOM degradation patterns. Concurrently, complex biogeochemical processes drove compositional convergence of DOM across natural aquatic systems. Identification of refractory DOM (RDOM) revealed substantially higher RDOM content in phytoplankton-dominated lakes compared to macrophyte-dominated lakes and urban rivers. These findings elucidate the molecular drivers of DOM degradation in inland waters and provide a theoretical framework for identifying labile and refractory DOM, thereby enabling assessment of the carbon source-sink functions and cycling processes in diverse inland aquatic ecosystems.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Yi Ren, University of Science and Technology Beijing (2410418486@qq.com)

Authors:

Yi Ren, University of Science and Technology Beijing  (2410418486@qq.com)

Shasha Liu, University of Science and Technology Beijing  (liushashajida@163.com)

Chengyu Suo, University of Science and Technology Beijing  (chengyu_suo@163.com)

Yunxuan Cheng, Chinese Research Academy of Environmental Sciences  (2410418486@qq.com)

Fengchang Wu, Chinese Research Academy of Environmental Sciences  (2410418486@qq.com)