Abstract：
As the largest reactive organic carbon pool, dissolved organic matter (DOM) plays an important role in various biogeochemical processes in lake ecosystems. Recently, climate change-induced extreme events (e.g., floods and droughts) have significantly modified the hydrological patterns of lakes worldwide, and regulated the quality and quantity of DOM. However, the responses of DOM chemistry to hydrological alteration in lakes remain poorly understood. Here we investigated the influences of hydrological alteration on sources, composition, and characteristics of DOM in Poyang Lake, the largest freshwater lake in China, using a combination of bulk chemical, optical and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) techniques. Results show various sources of DOM (autochthonous, allochthonous, and anthropogenic inputs) and significant variations in DOM chemistry across four hydrological periods (the retreating, dry, rising, and flooding periods) in Poyang Lake. During the retreating, rising, and flooding periods, DOM was characterized by higher aromaticity, humification degree, and recalcitrance, and exhibited pronounced allochthonous signatures. In contrast, DOM contained more S-containing molecules and aliphatic compounds during the dry period, displaying relatively stronger autochthonous features. Terrestrial inputs and the lignin-CHOS formation process are likely the primary underlying mechanisms shaping the differences in DOM chemistry in Poyang Lake. Our research demonstrates the significant impacts of hydrological alteration on DOM dynamics, and provides an improved understanding of DOM biogeochemical cycles and carbon cycling in large aquatic systems under global climate change.
摘要：
作为最大的反应性有机碳库，溶解有机质（DOM）在湖泊生态系统的各种生物地球化学过程中起着重要作用。最近,气候变化引起的极端事件(例如，洪水和干旱)显著改变了全球湖泊的水文模式，并规范了DOM的质量和数量。然而,DOM化学对湖泊水文变化的响应仍然知之甚少。在这里，我们研究了水文变化对水源的影响，composition,以及鄱阳湖DOM的特征，中国最大的淡水湖,使用散装化学品的组合，光学和傅里叶变换离子回旋共振质谱(FT-ICRMS)技术。结果显示DOM的各种来源(本地，异源的,和人为输入)以及四个水文时期DOM化学的显著变化(撤退，干,上升,和洪水时期）在鄱阳湖。在撤退期间，上升,和洪水时期，DOM的特点是芳香性较高，受辱程度,和顽抗，并表现出明显的异源特征。相比之下,DOM在干燥期间含有更多的含S分子和脂肪族化合物，表现出相对更强的本土特征。陆地输入和木质素-CHOS的形成过程可能是塑造鄱阳湖DOM化学差异的主要潜在机制。我们的研究证明了水文变化对DOM动力学的重大影响，并提供了对全球气候变化下大型水生系统DOM生物地球化学循环和碳循环的更好理解。
