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

我建议继续开展过去3.5年来开展的关于水中有机物质(OM)的形态、分布和保存的研究，以及使用分子代用品确定有机碳源和反应历史的研究。这项工作建立在以往证据的基础上，即沉积有机质的浓度和新鲜度与其物理形态、化学成分以及在从表层转移到深水和埋藏在沉积物中过程中对UV和O2的累积暴露有关。我们专门从事散体和分子方法的开发，以探索导致沉积物中有机质保存的因素的不同和经常相互矛盾的理论。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，特别是主要的非水解性O2敏感组分、黑碳组分、分子未表征组分和物理屏蔽组分，并探索它们的化学组成和在全球碳循环中的作用。将讨论以下主要问题：(1)海洋沉积物中保存的非水解性、黑碳和物理屏蔽组分的形式和微米级分布是什么？这些组分在缺氧和缺氧条件下对降解的敏感性是否不同？如果是这样，造成这种对比的物理和化学原因是什么？(2)矿物在深海中固定OM和保存海洋沉积物中不稳定的生物化学物质中的重要性是什么？(3)在碳和氧的生物地球化学循环中，烟尘/石墨黑碳保存的全球重要性是什么？(4)什么是化学物质，海洋溶解有机碳的绝大部分(50-75%)的同位素和分子(包括化合物特有的同位素)组成，在使用传统的超滤和固相萃取方法时，至今仍无法回收？

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?