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

我建议继续在过去三年半中开展的关于水生系统中有机物质（OM）的定量重要和未表征成分的形式、分布和保存的研究，以及使用分子代用物来确定有机碳源和反应历史的研究。这项工作建立在先前证据的基础上，即沉积OM的浓度和新鲜度与它们的物理形态、化学成分以及它们从表面到深水和埋藏在沉积物中的累积暴露于紫外线和氧气有关。我们专注于开发体积和分子方法，以探索有关沉积物中OM保存因素的不同且经常相反的理论。我们研究的主要目的是利用这些新开发的工具加深我们对沉积有机质定量重要组分保存控制的理解，特别是主要的不可水解o2敏感组分、黑碳、分子未表征组分和物理屏蔽组分，并探索它们的化学组成及其在全球碳循环中的作用。以下主要问题将得到解决：(1)保存在海洋沉积物中的非水解、黑碳和物理屏蔽组分的形式和微米尺度分布是什么？这些成分在有氧和无氧条件下是否表现出不同的降解敏感性，如果有，这些差异的物理和化学原因是什么？(2)矿物质在封存深海有机质和保存海洋沉积物中不稳定的生物化学物质方面的重要性是什么？(3)烟尘/石墨黑碳保存在碳氧生物地球化学循环中的全球重要性是什么？(4)绝大部分（50-75%）海洋溶解有机碳的化学、同位素和分子（包括化合物特定同位素）组成是什么？这些有机碳至今仍无法通过传统的超滤和固相萃取方法回收。

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?