Lushan Botanical Garden, Chinese Academy of Sciences, Jiujiang 332900, China.
Lushan Botanical Garden, Chinese Academy of Sciences, Jiujiang 332900, China.
Sci Total Environ. 2023 Jun 25;879:162999. doi: 10.1016/j.scitotenv.2023.162999. Epub 2023 Mar 24.
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 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.
江湖连通湖泊因其独特的水文模式而成为复杂且动态的生态系统，这可能会显著影响溶解有机物质（DOM）的产生、降解和转化过程，并进一步调节湖泊中 DOM 的化学性质。然而，江湖连通湖泊中 DOM 的分子组成和特征仍知之甚少。因此，本研究采用光谱技术和傅里叶变换离子回旋共振质谱（FT-ICR MS）探究了一个大型江湖连通湖泊（鄱阳湖）中 DOM 的光学性质和分子特征的空间变化。结果表明，鄱阳湖 DOM 化学性质具有高度的空间异质性（DOC 浓度、光学参数和分子化合物的变化），分子水平的多样性主要由杂原子化合物（含 N 和 S 的化合物）引起。与典型的湖泊和河流相比，江湖连通湖泊 DOM 的组成具有独特的特征（AI 和 DBE 值以及 CHOS 比例的差异）。此外，鄱阳湖南北部 DOM 的组成特征不同（如易降解性和分子化合物），这表明水文条件的变化可能会影响 DOM 的化学性质。另外，根据光学性质和分子化合物，可以一致地识别出 DOM 的各种来源（自生源、异生源和人为输入）。总的来说，本研究首次从分子水平上描述了鄱阳湖 DOM 的化学性质及其空间变化，这有助于我们更好地理解大型江湖连通湖泊系统中的 DOM。鼓励进一步研究不同水文条件下鄱阳湖 DOM 化学的季节性变化，以丰富江湖连通湖泊系统中碳循环的知识。
