基于FT-ICR-MS和感应纳喷雾离子化法辨析海洋沉积物DOM组分及厌氧降解机制

海洋次表层沉积物存在大量生物（深部生物圈）影响着地球最大碳库的储存，尚不清楚稳化保存的碳库如何支持生物在深层厌氧环境中存活并被降解。前期研究发现地热释放的沉积物溶解有机物（DOM）包括生物可利用组分及前体，可作为揭示该过程的突破口，但缺乏相应的分析方法。因此，本项目拟开展DOM分析方法探究，以海洋次表层沉积物DOM为研究对象，基于超高分辨质谱技术（FT-ICR-MS）新建提取方法，结合新型纳喷雾离子化技术以提高耐盐性，解决深层沉积物间隙水难以采集、目标信号损失的问题；然后通过受热培养实验，基于新建DOM分析方法辨明生物可利用中间产物以及厌氧降解过程的前体，探明厌氧降解的初始步骤，从而揭示地热作用下深部稳化碳库的活化机制，推动深部生物圈代谢机制的研究。该方法将开创性地实现沉积物DOM的高通量、小体积检测（样品量仅传统方法5%），为打开地球深部碳循环的黑匣子提供科学方法。

Marine subseafloor holds substantial amount of living biomasses (deep biosphere). These microbes might drive a slow but extensive carbon flow and play an important role in the carbon cycle in deep Earth and geochemical processes in upper hydrosphere. It is not clear how the microbes could survive on the old and recalcitrant organic matter (ROM) in subsurface sediments. Geothermal effect may cause the releasing of labile compounds from ROM. Dissolved organic matter (DOM) encompasses the analytical window for the initial degradation of ROM, while there is no suitable method to characterize the DOM of volume-limited pore water in deep subsurface sediments. Moreover, the conventional pretreatments of pore water via solid phase extraction induce selective loss of DOM. This project aims to develop a novel analytical technique for DOM from subsurface sediment by ultra-high-resolution mass spectrum (FT-ICR-MS). Firstly, different extraction techniques will be combined to reduce the selective loss of DOM, especially for the polar and small DOM, which are potentially bioavailable components for anaerobic bacteria or Archaea. After enrichment of DOM, nano-electrospray ionization (nano-ESI) will be applied. It enables a better ionization and signal of rapidly-cycled DOM in FT-ICR-MS with small sample volume and reduces the depression effect of ionization. Lastly, the novel method for DOM characterization will be applied for detection of labile compounds in cultivated sediments simulating the heated deep biosphere. The precursors and intermediates of labile DOM will be characterized for the investigation of initial step of degradation mechanism and thus the activation of refractory carbon pool. The sampling volume is reduced to 5%. The method will open a new window for rapidly-cycled DOM and the largely unknown initial step of degradation process in heated subsurface sediments. Therefore, this method suggests how the stabilized organic matter is transformed to bioavailable and cell-accessible components and throws new light on the ‘blackbox’ of microbe-involved carbon cycle in deep Earth.