A study of organic carbon dynamics in aquatic environments using bulk, molecular and compound-specific isotopic methods

我建议继续研究在过去的3.5年中发起的形式，分布和保存的定量重要的和未表征的成分的有机物（OM）在水生系统中，以及使用分子代理确定有机碳源和反应历史。这项工作建立在以前的证据表明，沉积有机质的浓度和新鲜度与它们的物理形式，化学成分和累积暴露于UV和O2从表面到深沃茨和埋藏在沉积物中的过境。我们专注于开发散装和分子方法，以探索不同的，往往是相反的理论，负责沉积物中有机质的保存因素。我们的研究的主旨是使用这些新开发的工具，以加深我们的理解控制沉积有机质的数量上的重要组成部分的保存，特别是占主导地位的非水解O2敏感，黑碳，分子未表征，物理屏蔽馏分，并探讨其化学组成和在全球碳循环中的作用。主要研究内容如下：（1）海洋沉积物中保存的不可水解的黑碳和物理屏蔽组分的形态和微米级分布特征是什么？这些成分在好氧和缺氧条件下对降解是否表现出不同的敏感性，如果是，造成这种差异的物理和化学原因是什么？(2)矿物在深海有机质的封存和海洋沉积物中不稳定生物化学物质的保存方面的重要性是什么？(3)在碳和氧的地球化学循环中，烟灰/石墨黑碳保存的全球重要性是什么？(4)海洋溶解有机碳的绝大部分（50-75%）至今仍无法用传统的超滤和固相萃取方法回收，其化学、同位素和分子（包括特定化合物的同位素）组成是什么？

I propose to continue research initiated in the past 3.5 years on the forms, distributions and preservation of quantitatively important and uncharacterized components of organic matter (OM) in aquatic systems, as well as on the use of molecular proxies for determining organic carbon sources and reaction histories. This work builds on previous evidence that the concentration and freshness of sedimentary OM are related to their physical forms, chemical compositions and cumulative exposure to UV and O2 during their transit from the surface to deep waters and burial in sediments. We are specializing in the development of bulk and molecular methods to probe the different and often opposing theories on the factors responsible for the preservation of OM in sediments. The main thrust of our research is to use these newly developed tools to deepen our understanding of the controls on the preservation of quantitatively important components of sedimentary OM, especially the predominant non-hydrolysable O2-sensitive, black carbon, molecularly-uncharacterized, and physically shielded fractions, and to probe their chemical composition and role in the global carbon cycle. The following major questions will be addressed: (1) What are the forms and micron-scale distributions of the non-hydrolysable, black carbon and physically shielded components preserved in marine sediments? Do these components exhibit different sensitivities to degradation under oxic versus anoxic conditions, and if so, what are the physical and chemical reasons for these contrasts? (2) What is the importance of minerals in the sequestration of OM in the deep ocean and in the preservation of labile biochemicals in marine sediments? (3) What is the global importance of soot/graphitic black carbon preservation in the biogeochemical cycles of carbon and oxygen? (4) What is the chemical, isotopic and molecular (including compound-specific isotopes) composition of the overwhelming fraction (50-75%) of marine dissolved organic carbon that still today is not recovered when using the traditional ultrafiltration and solid-phase extraction methods?