Organic carbon cycling and preservation in aquatic environments: Origin, forms and mechanisms using bulk, molecular and isotopic methods

我建议继续过去5年开始的关于水环境中数量上重要的有机物(OM)的形式、来源、反应和命运的研究。我们计划的中心主题是开发可以应用于有机混合物的新的分析方法(体积、分子和同位素)，并使用这些方法来检验关于影响水生系统中OM循环的过程的假设。在上一个DG循环中，我们的工作针对的是活性铁氧化物和沉积OM之间的相互作用，以及这些相互作用在沉积物中碳保存方面所起的作用。我们还开发了测量海水中溶解有机碳的13C特征的方法和优化的仪器，并利用甲烷的稳定同位素特征来破译其在地下水中的来源，以及在湖泊沉积物中的循环。未来5年提出的研究将回答我们以前工作提出的一些问题，并描述下一个DG周期将开展的新的和原创的项目。 未来5年，我们将主要讨论以下主题：(1)我们现在将针对沉积物中铁硫化物与OM之间的相互作用，及其在OM循环和保存中的作用；(2)我们将探索溶解硫化物暴露对自由和OM结合的铁氧化物的影响和机制；(3)我们将评估从缺氧沉积物中提取的天然孔隙水对硫化铁颗粒的反应性，并研究相应固相中硫化物的形态；(4)我们将使用分子模拟和单分子原子力显微镜来更好地了解有机化合物与硫化铁纳米颗粒表面的相互作用；(5)在一项新的举措中，我们将利用对石油衍生碳氢化合物的特定化合物稳定同位素分析(CSIA；13C和D)来了解风化作用(例如，扩散、蒸发、光氧化和生物降解)对这些碳氢化合物的相对丰度和稳定同位素特征的影响，我们将建立一个稀释模型，以便能够在空间和时间上追踪圣劳伦斯河、河口和海湾中的这些污染物；以及(6)我们将在一系列小项目中继续开发我们的CSIA方法工具箱，CSIA的应用可能对这些项目有所裨益。 从机械上理解氧化还原界面上屏蔽的OM的动力学是生物地球化学中仍然存在的最大分析前沿之一。因此，制定新的分析战略是从机械上了解湖泊、河口和海洋有机质保存的基本前提。特别是我们在OM与Fe硫化物相互作用方面的工作将被证明是非常有前途的。

I propose to continue research initiated in the past 5 years on the forms, sources, reactions, and fates of quantitatively important forms of organic matter (OM) in aquatic environments. The central themes of our program are to develop new analytical methods (bulk, molecular and isotopic) that can be applied to organic mixtures, and to use these methods to test hypotheses about processes affecting OM cycling in aquatic systems. During the previous DG cycle, our work targeted the interactions between reactive iron oxides and sedimentary OM and the role played by these interactions on carbon preservation in sediments. We also developed methods and optimized instrumentation for the measurement of the 13C signature of dissolved organic carbon in seawater, and used the stable isotope signature of methane to decipher its sources in ground water, and its cycle in lacustrine sediments. The research proposed in the next 5 years will answer some of the questions that were raised by our previous work, and describes new and original projects that will be undertaken during the next DG cycle. The following major themes will be addressed in the next 5 years: (1) we will now target the interactions between iron sulfides and OM in sediments, and their role in OM cycling and preservation; (2) we will probe the effect and mechanism of dissolved sulfide exposure on free and OM-bound iron oxides; (3) we will assess the reactivity of natural pore water extracted from anoxic sediments for iron sulfide particles and examine the speciation of sulfides in the corresponding solid phase; (4) we will use molecular modeling and single molecule atomic force microscopy to better understand the interactions between organic compounds and the surface of iron sulfides nanoparticles; (5) in a new initiative, we will use compound-specific stable isotope analysis (CSIA; 13C and D) on petroleum derived hydrocarbons to understand the effect of weathering (e.g., dispersion, evaporation, photooxidation and biodegradation) on the relative abundances and stable isotope signatures of these hydrocarbons, and we will build a dilution model that will allow spatially and temporally tracking these contaminants in the St. Lawrence River, Estuary and Gulf; and (6) we will keep developing our CSIA methods toolbox in a series of small projects for which the application of CSIA could be rewarding. Mechanistically understanding the dynamics of shielded OM at the redox interface represents one of the greatest analytical frontiers remaining in biogeochemistry. Developing new analytical strategies is thus a fundamental prerequisite for obtaining a mechanistic understanding of OM preservation in lakes, estuaries and the ocean. Our work on OM interactions with Fe sulfides, in particular, will prove very promising.