Radiocarbon as a Tool for Studying Organic Matter Diagenesis in Rapidly Accumulating, Continental Margin Sediments: Linking Bulk Organic Matter and Molecular Level Studies

沉积物中的有机质氧化在广泛的地球化学循环中起着核心作用。尽管在有机地球化学和孔隙水采样和模拟方面的最新进展提高了我们对这一过程的理解，但海洋地球化学家对沉积成岩作用的定量模式还没有取得令人满意的描述。伍兹霍尔海洋研究所的研究人员将开展研究，通过溶质和固体成分测量与溶解和固相C的碳同位素组成(稳定C和放射性碳)的测定相结合，促进我们对大陆边缘沉积物中有机质氧化的定量理解。该项目将与T.Eglinton博士合作进行，他目前正在进行一个项目，研究大陆边缘沉积物中特定有机化合物的浓度和放射性碳年龄。通过他们的共同努力，研究人员计划以其他方式不可能的方式来检验有机地球化学工作产生的假说。他们将集中在三个领域开展工作：(1)使用放射性碳作为研究边缘沉积物中有机质氧化的示踪剂，(2)检验放射性碳测年的难降解有机化合物的分布可用于推断沉积物沉积后运移的假设，(3)将生物扰动混合速率和机制的测量添加到Eglinton小组对特定有机化合物向下岩心剖面的测量中，以计算一系列反应性。由此产生的无机和有机相结合的观点将提供一个实质性的步骤，超越在底栖生物地球化学中已经成为常态的单独的有机和无机研究。他们还将在两个地点进行详细的溶质和固相测量工作：W站，用于监测物理海洋学参数和颗粒浓度的系泊地点，以及一组系泊沉积物陷阱，位于马萨诸塞州南部3000米深的地方；以及哈特拉斯角外大西洋中部海湾储存中心的一个对比地点。就更广泛的影响而言，开发模型研究海洋地球化学循环在全球碳和营养收支中的作用是解释过去气候变化和预测未来变化的关键部分。该项目将通过收集新数据和审查解释数据的新方法来促进模型的开发。它还将为研究生和本科生提供研究机会。此外，PIS将在他们教授的研究生水平的沉积物地球化学课程中使用这一项目的结果。

ABSTRACTOCE-0526389Organic matter oxidation in sediments plays a central role in a wide range of geochemical cycles. Although recent advances in organic geochemistry and pore water sampling and modeling have led to improvements of our understanding of the process, marine geochemists have not yet achieved a satisfactory description for quantitative models of sedimentary diagenesis.In this project, researchers at the Woods Hole Oceanographic Institution will conduct studies to advance our quantitative understanding of organic matter oxidation in continental margin sediments through the combination of solute and solid composition measurements with determinations of the carbon isotopic composition (stable C and radiocarbon) of dissolved and solid phase C. The project will be carried out in collaboration with Dr. T. Eglinton who is currently undertaking a project to study the concentration and radiocarbon age of specific organic compounds in continental margin sediments. Through their combined efforts, the researchers plan to examine hypotheses arising from the organic geochemical work in ways that would not otherwise be possible. They will focus the effort in 3 areas: (1) The use of radiocarbon as a tracer for investigating organic matter oxidation in margin sediments, (2) Examination of the hypothesis that distributions of radiocarbon-dated, refractory organic compounds can be used to infer post-depositional transport of sediments, (3) Adding measurements of bioturbation mixing rates and mechanisms to the Eglinton group's measurements of downcore profiles of specific organic compounds to calculate a suite of reactivities. The resulting combined inorganic and organic perspective will provide a substantial step beyond the separate organic and inorganic studies that have been the norm in benthic geochemistry. They will also carry out work with detailed solute and solid phase measurements at two locations: Station W, the location of moorings for monitoring physical oceanographic parameters and particle concentrations as well as a set of moored sediment traps, which is located at a depth of 3000m, south of Massachusetts; and a contrasting site at the Mid-Atlantic Bight depocenter off Cape Hatteras.In terms of broader impacts, the development of models to examine the role of marine geochemical cycles in global carbon and nutrient budgets is a key part of efforts to explain past climate changes and forecast future changes. This project will contribute to model development through both the collection of new data and the examination of new ways to interpret the data. It will also provide research opportunities for graduate and undergraduate students. In addition, the PIs will use results from this project in the graduate level Sediment Geochemistry course that they teach.