Xiaoqian Zhan, Hongyan Bao, Jutta Niggemann, Weiqiang Zhao, Nengwang Chen, Dekun Huang, Moge Du, Yuanbi Yi, Thorsten Dittmar, Shuh-Ji Kao
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引用次数: 0
Abstract
The export of dissolved organic matter (DOM) from rivers is essential for linking terrestrial and marine carbon reservoirs in the global carbon cycle. However, there is limited knowledge regarding how the molecular composition of riverine DOM changes under different hydrological conditions, especially during extreme rainfall events. Moreover, the factors beyond hydrology that impact DOM composition have not been well defined. To address these gaps, samples were collected from a human-impacted medium-sized subtropical monsoonal river across various hydrological conditions throughout a complete hydrological cycle. Utilizing high-resolution mass spectrometry, it was discovered that the solid-phase extractable DOM (SPE-DOM) during the high-flow (1 < runoff (Q): annual mean runoff (Qm) < 3) and extreme-rain (Q:Qm > 3) periods exhibited a higher number of molecular formulae, lower H/C, higher O/C, and a higher proportion of carboxylic-rich alicyclic molecules compared to the low-flow period (LFP) (Q:Qm < 1). These alterations were attributed to input from more diverse sources, particularly a greater input from soil organic matter with higher oxidation degrees. Additionally, the P-containing formulae were more enriched during the extreme-rain period, likely from agricultural lands and sediment release. Conversely, the fraction of S-containing formulae was significantly higher during the LFP, possibly due to the amplified influence of anthropogenic input. Furthermore, the DOM aromaticity did not fluctuate with runoff but was significantly associated with temperature. In summary, the study indicated that the composition of DOM varied significantly under different hydrological conditions, with temperature and anthropogenic activities identified as crucial factors influencing riverine DOM export.
河流溶解有机物(DOM)的输出对于连接全球碳循环中的陆地和海洋碳库至关重要。然而,对于河流溶解有机物的分子组成在不同水文条件下,尤其是在极端降雨事件期间如何变化,人们的了解还很有限。此外,除水文因素外,影响 DOM 组成的其他因素也没有得到很好的界定。为了填补这些空白,研究人员从一条受人类影响的中型亚热带季风河流中采集了样本,这些样本跨越了整个水文周期中的各种水文条件。利用高分辨率质谱分析发现,与小流量时期(LFP)(Q:Qm <1)相比,大流量时期(1 <径流(Q):年平均径流(Qm)<3)和极端降雨时期(Q:Qm >3)的固相可萃取 DOM(SPE-DOM)表现出更多的分子式、更低的 H/C、更高的 O/C,以及更高的富含羧基的脂环族分子比例。这些变化归因于来自更多样化来源的输入,特别是来自氧化度更高的土壤有机物的更大输入。此外,在极端降雨期,含磷公式更加富集,这可能来自农田和沉积物的释放。相反,在低纬度雨季,含 S 配方的比例明显较高,这可能是由于人为输入的影响扩大了。此外,DOM芳香度并不随径流波动,但与温度有显著关联。总之,研究表明,在不同的水文条件下,DOM 的组成变化很大,温度和人为活动被认为是影响河流 DOM 出口的关键因素。
期刊介绍:
JGR-Biogeosciences focuses on biogeosciences of the Earth system in the past, present, and future and the extension of this research to planetary studies. The emerging field of biogeosciences spans the intellectual interface between biology and the geosciences and attempts to understand the functions of the Earth system across multiple spatial and temporal scales. Studies in biogeosciences may use multiple lines of evidence drawn from diverse fields to gain a holistic understanding of terrestrial, freshwater, and marine ecosystems and extreme environments. Specific topics within the scope of the section include process-based theoretical, experimental, and field studies of biogeochemistry, biogeophysics, atmosphere-, land-, and ocean-ecosystem interactions, biomineralization, life in extreme environments, astrobiology, microbial processes, geomicrobiology, and evolutionary geobiology