COLLABORATIVE RESEARCH: The Oxidation of Kerogen During Weathering

9804781伯纳尔地球化学碳循环对地球大气（Po 2，Pco 2）在地质时间尺度上的演变产生重大影响。 作为这个循环的一部分，沉积有机物[SOM]的氧化包括超过80%的总耗氧量，以维持一个均衡的Po 2。 然而，很少有以前的努力已经检查的途径，效率或SOM氧化率，因此在地球化学碳循环的整个环节仍然很难定义。 有机物氧化为二氧化碳被认为是一个整体的长期风化过程，常见的表达式CH 2 O + O2 CO2 +H2O意味着作用于均质物质的单步反应。 事实上，SOM是复杂和多相的，因此氧化可能通过一系列尚未定义的中间产物和在转化为无机碳之前的连续氧化反应进行。 因此，为了更好地了解SOM氧化的过程中，这些结构和组成的详细表征在不同阶段的SOM oxidations.This研究提出了调查的途径，速率和效率的化学风化的有机物中所含的黑色页岩表征吸收氧气和其他氧化/风化反应，改变SOM的分子结构。 样品已经沿着富含有机碳的岩石上发育的风化剖面采集。 所选地层（绿色河、伍德福德、新奥尔巴尼和蒙特雷）代表矿物学和有机质类型的特定端员。 因此，本研究的结果将揭示渐进风化的SOM序列，并指出岩性和有机质类型可能在定义这个序列中发挥的作用。 SOM风化的速率将通过比较剖面之间的黄铁矿损失和检查已知年龄的剖面来限制。 六个页岩剖面的初步结果表明，在风化过程中，在3-5米的距离内，总有机碳损失了70-90%。 残留有机质的小，但显着的质量仍然在每个配置文件的表面，这意味着不完整的SOM矿化效率。 对风化剖面的进一步分析将确定有机物的元素、同位素和岩相组成，沿着页岩矿物学和粒度和渗透率等物理数据。 有机地球化学分析工具，特别是核磁共振，红外光谱和快速热解与气相色谱-质谱联用，将用于破译分子水平的结构特征，如碳骨架类型和含氧功能。 14 C测年将用于区分现代土壤碳污染的样品。通过研究土壤有机质风化的速率、效率和途径以及残余物的供应，（放射性碳死）有机质到当代有机碳库（土壤、湖泊和/或海洋沉积物），这项研究将对地球科学的几个学科产生有价值的影响，包括化学海洋学，表层地球化学，地球化学循环模拟、环境地球化学和第四纪地质。 该项目的协作性质和所采用的分析工具，化学技术和数值方法的范围将为参与该项目的研究生和本科生提供坚实的经验和知识基础。 SOM风化的这项研究（包括项目的开发和本提案的准备）包括博士学位的重要组成部分。论文研究的研究生，史蒂芬佩奇，并列入研究的本科生将加强双方的教育和研究。

9804781BernerThe geochemical carbon cycle exerts a major influence on the evolution of Earth's atmosphere (Po2, Pco2) over geologic time scales. As part of this cycle, oxidation of sedimentary organic matter [SOM] comprises more than 80% of the total oxygen consumption required to maintain an equable Po2. However, little prior effort has been made to examine the pathways, efficiency or rates of SOM oxidation, and thus an entire link in the geochemical carbon cycle remains poorly defined. Oxidation of organic matter to carbon dioxide is assumed to be the overall, long-term weathering process, with the common expression CH2O +O2CO2+H2O implying a single-step reaction acting on an homogeneous material. The reality is that SOM is complex and heterogeneous, so that oxidation likely proceeds through an as yet undefined series of intermediate products and sequential oxidation reactions prior to conversion to inorganic carbon. Thus, to better understand the process of SOM oxidation, detailed characterization of these structures and compositions obtained at various stages of SOM oxidation is required.This study proposes to investigate the pathways, rates and efficiency of the chemical weathering of organic matter contained in black shales by characterizing uptake of oxygen and other oxidation/weathering reactions, which alter the molecular structure of SOM. Samples have already been collected along weathering profiles developed on organic carbon-rich rocks. The selected formations (Green River, Woodford, New Albany, and Monterey) represent specific end-members of mineralogy and organic matter type. Thus, the results of this study will both reveal the sequence of progressively weathered SOM, and indicate the role that lithology and organic matter type may play in defining this sequence. The rate of SOM weathering will be constrained by comparing pyrite loss between profiles and by examining profiles of known age. Preliminary results from six shale profiles indicate between 70-90% loss of total organic carbon across a distance of 3-5 m during weathering. A small but significant mass of relict organic matter remains at the surface of each profile, implying incomplete SOM remineralization efficiency. Further analyses of the weathering profiles will determine elemental, isotopic and petrographic composition of the organic matter, along with shale mineralogy and physical data such as grain size and permeability. Organic geochemical analytical tools, specifically nuclear magnetic resonance, infrared spectroscopy, and flash pyrolysis in tandem with gas chromatography-mass spectrometry, will be used to decipher molecular level structural characteristics such as carbon skeleton types and oxygen-containing functionality. 14C age dating will be used to distinguish samples contaminated by modern soil carbon.By addressing the rate, efficiency and pathways of SOM weathering and supply of relict (radiocarbon dead) organic matter to contemporary organic carbon reservoirs (soils, lacustrine and/or marine sediments), this study will have a valuable impact on several disciplines of the Earth sciences including chemical oceanography, surficial geochemistry, geochemical cycle modeling, environmental geochemistry, and Quaternary geology. The collaborative nature of the project and the range of analytical tools, chemical techniques and numerical methods employed will generate a solid foundation of experience and knowledge for graduate students and undergraduates involved in this project. This study of SOM weathering (including development of the project and preparation of this proposal) comprises a crucial part of the Ph.D. thesis research for a graduate student, Steven Petsch, and the inclusion of undergraduates in the research will enhance both their education and the research.