题目 Title

Optical and molecular diversity of dissolved organic matter in sediments of the Daning and Shennong tributaries of the Three Gorges Reservoir.

期刊 Journal

Frontiers in Environmental Science (IF=4.6)

作者 Author

Wang K; Fang HW; He GJ; Huang L; Cui ZH; Gao QF; Xu S; Wang DC; Wu XH; He D

摘要 Abstract

Introduction: Damming significantly modifies the function of natural river networks and influences sediment dynamics with a reservoir's operation. The dissolved organic matter (DOM) in reservoir sediments severely affects carbon flow from land to sea. However, the properties of DOM (e.g., quantity and quality) in reservoir sediments and their relationship with carbon cycling remain unclear as complex reservoir construction interrupts the environmental processes.Methods: This study characterizes the optical and molecular properties of sediment water-extractable organic matter (WEOM) in the Daning and Shennong tributaries of the world's largest reservoir-the Three Gorges Reservoir (TGR)-by applying optical techniques and ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS).Results and Discussion: We first assessed the link between light-absorbing components and the individual molecules in WEOM, which were significantly different than DOM in water and indicated that there might be an intrinsic variation between DOM in sediment and in water. Then, with the unique optical-molecular property linkage assessed, multiple sources (autochthonous and terrestrial) were identified, and a declining trend of terrestrial and recalcitrant WEOM was revealed from the tributaries upstream to downstream. Finally, through covariance analysis of the properties between WEOM and sediment particles, we demonstrated that the WEOM dynamic was most likely regulated by hydrologic sorting-induced particle size and mineral composition variations of sediment. Moreover, assessment between lability and WEOM molecular properties suggested that the WEOM dynamic likely contributes to carbon burial in the reservoir. This study emphasizes the influence of dam construction on organic matter accumulation and riverine carbon cycling.

简介 Brief introduction

水库的建设显著改变了自然河网的功能，水库的运行也影响了底泥的运动规律。从陆地到海洋的碳流会受底泥中的可溶性有机质（DOM）的影响，然而，因为复杂的水库建设中断了自然过程，水库底泥中 DOM 的特性（如数量和质量）及其与碳循环的关系尚不明晰。本研究旨在应用光学技术和超高分辨率傅立叶变换离子回旋共振质谱（FT-ICR MS），分析世界上最大的水库--三峡水库（TGR）的大宁河和神农溪支流的底泥中水可提取有机物（WEOM）的光学和分子特性。
首先，我们考察了WEOM中的吸光成分与个体分子之间的联系，结果表明底泥中的DOM与水中的DOM可能存在固有差异。随后，通过光学-分子性质的相关性，确定了WEOM的多种来源（自生和陆生），并观察到陆生和难降解WEOM从支流上游到下游呈下降趋势。最后，通过对WEOM与底泥颗粒之间的特性的协方差分析，我们阐明了水文分选引起的底泥颗粒大小和矿物成分变化调控了WEOM的运动。此外，对易变性和 WEOM 分子特性之间的分析表明，WEOM 的运动可能有助于水库中的碳埋藏。本研究强调了水库建设对有机物积累和河流碳循环的影响。

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