Micro- and Nanofabric Protection of Organic Matter in Clay-rich Muds and Polychaete Fecal Pellets: Direct Visualization by TEM and Quantitative Analysis

知识价值。本研究采用新颖的技术，利用透射电子显微镜（TEM）在纳米和微结构特征中可视化三维有机质，解决了海洋富粘土沉积物和土壤中有机质保存的挑战性问题。这项工作将促进对过程和机制以及纳米和微结构特征的理解，这些特征在海洋沉积物的早期发展过程中驱动这些尺度上的OM保存。它将提供直接的“前沿”证据，证实或反驳科学界在没有直接观测证据的情况下提出的关于海洋沉积物中微生物保存的概念和想法。它将提供直接的视觉证据，以防止粘土织物对OM的酶解。有待验证的假设包括：(1)孔喉和孔隙的扭曲阻碍了酶通过粘土织物的运动；(2)OM优先吸附在粘土薄片的边缘和粘土结构域交界处的间隙上。假设检验需要建立一个现实的定量三维可视化OM保护模型，该模型基于特定底物的潜在酶解和直接透射电镜观察，这些观察与代表全球最重要OM沉积中心的沉积物系列剖面重建的孔隙有关。粘土本身是电子密集的，很容易通过TEM可视化；OM的可视化将通过电子致密染色来完成。蒙脱石和伊利石粘土样品将被研究，包括从海洋多毛体中收集的粪便颗粒。本研究将基于有机-粘土关系的直接可视化和定量分析，推动有机质保存和有机碳循环的现实概念模型的发展。该研究还将为以下方面提供定量数据：(1)了解海洋沉积物中有机碳的生物地球化学通量；(2)开发新兴的有机粘土保存动力学模型。更广泛的影响。来自南密西西比大学（USM）的一名研究生将接受TEM技术和图像分析方面的培训，将参与撰写手稿，并在区域和国家科学会议上展示数据。在我们的常规夏季教学计划中，将为科学教育研究生提供TEM技术和图像分析方面的培训。通过当地NSF REU项目的本科生将协助TEM工作和图像分析，并在当地和区域会议上展示研究成果。该项目支持EPSCoR州的两个机构的三名研究人员，并与学术界和私营部门的copi建立学科和机构之间的合作。研究成果将在主要国际期刊以及地方和国家专业会议上发表。将建立一个网站，广泛提供我们的数据和解释。该项目通过增加对早期沉积成岩过程中有机质封存的认识，以及了解原干酪根和烃源岩中干酪根的发育，具有更广泛的社会和经济意义。

Intellectual Merit. This research addresses challenging issues of organic matter (OM) preservation in marine clay-rich sediment and soils using novel techniques for visualizing three dimensionally OM in nano- and microfabric signatures using transmission electron microscopy (TEM). This effort will advance the understanding of processes and mechanisms and nano- and microfabric signatures that drive OM preservation at these scales during the very early development of marine sediment. It will provide direct "cutting edge" evidence confirming or refuting concepts and ideas advanced without direct observational evidence by the scientific community concerning OM preservation in marine sediment. It will provide direct visual evidence of protection against enzymatic digestion of OM by clay fabric. Hypotheses to be tested include, (1) pore throats and tortuosity of pores impedes the movement of enzymes through clay fabric and (2) OM is preferentially sorbed onto edges of clay platelets and interstices at the junctures of clay domains. Hypothesis testing entails developing a realistic quantitative three-dimensional visual model of OM protection based on potential enzymatic digestion of specific substrates and direct TEM observations of OM distribution with respect to pores reconstructed from serial sections of sediments representing the globally most important OM depocenter. Clay is inherently electron dense and easily visualized by TEM; visualization of OM will be accomplished with electron dense stains. Smectite and illite clay samples will be studied including field collected fecal pellets from marine polychaetes. This research will advance the development of realistic conceptual models of OM preservation and ultimately organic carbon cycling based on direct visualization of organo-clay relationships and quantitative analysis. The research will also provide quantitative data for advancing (1) understanding of biogeochemical fluxes of organic carbon in marine sediments and (2) the development of emerging models addressing organo-clay preservation dynamics.Broader Impacts. A graduate student from the University of Southern Mississippi (USM) will be trained in TEM techniques and image analysis, will participate in writing manuscripts, and in presenting data at regional and national scientific meetings. Training will be offered to science education graduate students in TEM techniques and image analysis during our regular summer teaching program. Undergraduates through the local NSF REU program will assist in TEM work and image analysis and present research at local and regional meetings. The project supports three investigators at two institutions in an EPSCoR state and establishes collaboration among disciplines and institutions with CoPIs from academia and the private sector. Research results will be published in leading international journals as well as local and national professional meetings. A website will be established to make our data and interpretations widely available. This project has broader societal and economic implications by increasing knowledge of OM sequestration during early sediment diagenesis and understanding the development of protokerogen and ultimately kerogen in petroleum source rocks.