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

智力上的功绩。这项研究解决了富含粘土的海洋沉积物和土壤中有机质(OM)保存的挑战性问题，使用新技术利用透射电子显微镜(TEM)在纳米和微结构特征中三维显示有机物(OM)。这一努力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非常早期的发展过程中推动了这些规模的有机质保存。它将提供直接的“尖端”证据，证实或驳斥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有机质保存的概念和想法。这将为防止粘土织物对OM的酶消化提供直接的视觉证据。有待检验的假说包括：(1)孔喉和毛孔的弯曲阻碍了酶在粘土织物中的运动；(2)OM优先吸附在粘土微片的边缘和粘土结构域交界处的空隙上。假设检验需要开发一个现实的、定量的OM保护三维可视化模型，该模型基于对特定底物的潜在酶消化，以及相对于代表全球最重要的OM沉积中心的连续沉积物切片重建的孔的OM分布的直接透射电子显微镜观察。粘土本质上是电子密集型的，很容易用电子显微镜可视化；OM的可视化将通过电子密集型染料来完成。蒙脱石和伊利石粘土样本将被研究，包括从海洋多毛类动物现场收集的粪便颗粒。这项研究将在有机粘土关系的直接可视化和定量分析的基础上，推动有机质保存和最终有机碳循环的现实概念模型的发展。这项研究还将为促进(1)理解海洋沉积物中有机碳的生物地球化学通量和(2)研究有机粘土保存动力学的新兴模型的发展提供定量数据。南密西西比大学(USM)的一名研究生将接受瞬变电磁技术和图像分析方面的培训，将参与撰写手稿，并在地区和国家科学会议上展示数据。在我们的常规暑期教学计划中，将为科学教育研究生提供瞬变电磁技术和图像分析方面的培训。通过当地NSF REU计划的本科生将协助瞬变电磁工作和图像分析，并在当地和地区会议上展示研究。该项目支持EPSCoR州两个机构的三名调查人员，并与学术界和私营部门的COPI建立了学科和机构之间的合作。研究成果将发表在领先的国际期刊以及地方和国家专业会议上。将建立一个网站，广泛提供数据和解释。该项目通过增加对早期沉积物成岩作用中有机质封存的认识，了解油源岩中原干酪根并最终干酪根的发育，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 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.