Exploring the optical properties and molecular characteristics of dissolved organic matter in a large river-connected lake (Poyang Lake, China) using optical spectroscopy and FT-ICR MS analysis

• Published in: The Science of the total environment 2023-06, Vol.879, p.162999-162999, Article 162999
• Main Authors: Xu, Lei, Hu, Qian, Jian, Minfei, Mao, Kai, Liu, Zetian, Liao, Wei, Yan, Yumei, Shen, Ruichang, Zhong, Aiwen
• Format: Article
• Language: English
• Subjects: Dissolved organic matter; FT-ICR MS; Molecular characteristics; Optical properties; Poyang Lake; River-connected Lake
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.162999

River-connected lakes are complicated and dynamic ecosystems due to their distinctive hydrological pattern, which could significantly impact the generation, degradation, and transformation processes of dissolved organic matter (DOM) and further regulate DOM chemistry in lakes. However, the molecular compositions and characteristics of DOM in river-connected lakes are still poorly understood. Thus, here the spatial variations of optical properties and molecular characteristics of DOM in a large river-connected lake (Poyang Lake) were explored via spectroscopic techniques and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results showed high degree of spatial heterogeneity of DOM chemistry (variations in DOC concentrations, optical parameters, and molecular compounds) in Poyang Lake, and the diversity at the molecular level was primarily caused by the heteroatom compounds (N- and S- containing). Compared with classic lakes and rivers, DOM compositions of the river-connected lake had distinctive characteristics (differences in the AImod and DBE values, and CHOS proportions). And the composition characteristics of DOM between the southern and northern parts of Poyang Lake were different (such as the lability and molecular compounds), suggesting the changes of hydrologic conditions may affect the DOM chemistry. In addition, various sources of DOM (autochthonous, allochthonous, and anthropogenic inputs) were identified agreeably based on optical properties and molecular compounds. Overall, this study first characterizes the DOM chemistry and reveals its spatial variations in Poyang Lake at the molecular level, which could improve our understanding of DOM in large river-connected lake systems. Further studies are encouraged to investigate the seasonal variations of DOM chemistry under different hydrologic conditions in Poyang Lake to enrich the knowledge of carbon cycling in river-connected lake systems. [Display omitted] •The first molecular-level study on spatial heterogeneity of DOM in Poyang Lake•Diversity of DOM revealed at the molecular level mainly by S- and N-containing formulas•Different DOM chemistry between parts of different hydrological conditions•Autochthonous, allochthonous and anthropogenic sources of DOM were identified in Poyang Lake.