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

Lei Xu; Qian Hu; Minfei Jian; Kai Mao; Zetian Liu; Wei Liao; Yumei Yan; Ruichang Shen; Aiwen Zhong

doi:10.1016/j.scitotenv.2023.162999

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

Sci Total Environ. 2023 Jun 25:879:162999. doi: 10.1016/j.scitotenv.2023.162999. Epub 2023 Mar 24.

Authors

Lei Xu¹, Qian Hu², Minfei Jian³, Kai Mao², Zetian Liu², Wei Liao⁴, Yumei Yan², Ruichang Shen⁵, Aiwen Zhong⁶

Affiliations

¹ Lushan Botanical Garden, Chinese Academy of Sciences, Jiujiang 332900, China. Electronic address: xul@lsbg.cn.
² Lushan Botanical Garden, Chinese Academy of Sciences, Jiujiang 332900, China.
³ College of Life Science, Jiangxi Provincial Key Laboratory of Protection and Utilization of Subtropical Plant Resources, Jiangxi Normal University, Nanchang 330022, China.
⁴ Wetland Research Center, Jiangxi Academy of Forestry, Nanchang 330032, China.
⁵ Jiangxi Province Key Laboratory of Watershed Ecosystem Change and Biodiversity, Center for Watershed Ecology, Institute of Life Science, Nanchang University, Nanchang 330031, China; Jiangxi Poyang Lake Wetland Conservation and Restoration National Permanent Scientific Research Base, National Ecosystem Research Station of Jiangxi Poyang Lake Wetland, Nanchang University, Nanchang 330031, China.
⁶ Lushan Botanical Garden, Chinese Academy of Sciences, Jiujiang 332900, China. Electronic address: zhongaw@lsbg.cn.

PMID: 36966846
DOI: 10.1016/j.scitotenv.2023.162999

Abstract

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 AI_mod 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.

Keywords: Dissolved organic matter; FT-ICR MS; Molecular characteristics; Optical properties; Poyang Lake; River-connected Lake.