EAR-PF: Light- and Iron-Mediated Oxidation Mechanisms of Organic Matter

Claresta Joe-Wong博士获得了劳伦斯伯克利国家实验室的博士后奖学金，研究大气和内陆水域之间的碳循环，由于全球气候变化，这一研究越来越重要。内陆水域是全球碳循环的重要组成部分，因为它们将有机碳从土壤输送到海洋；把它埋在沉积物中；并以二氧化碳的形式释放，然而内陆水域将有机碳氧化成二氧化碳的自然过程还没有被很好地理解。该项目将描述这些过程中最重要但约束较差的过程之一，即当铁存在时，溶解的有机碳在阳光下的氧化。这项研究将分子水平上的这些机制与广泛的气候变化联系起来，将用于指导将化学原理与地球科学过程联系起来的本科课程计划。本科生将参与暑期研究实习，并接触到地球科学领域的创新技术。博士后将受益于拓宽她的研究视角和方法，以及为她未来的职业生涯获得的指导经验。与铁络合可以增强有机碳对光的反应活性，从而释放出二氧化碳。然而，过多的涉及短寿命自由基中间体的氧化途径使得预测铁的作用变得困难。本研究将利用亚皮秒分辨率的超快光谱技术对铁介导的光氧化反应机理和反应中间体进行实验表征。模型羧酸盐光反应性的光谱表征将与实验室实验相结合，确定从科罗拉多州东河流域和阿拉斯加北极长期生态研究基地收集的溶解有机碳的铁介导光解动力学和产物。最终，将溶解有机碳的光氧化机制理解与碳通量的大尺度模型相结合，可能会促进碳动力学的更全面的概念框架。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Dr. Claresta Joe-Wong has been awarded a postdoctoral fellowship to work at Lawrence Berkeley National Laboratory on understanding carbon cycling between the atmosphere and inland waters, which is of increasing importance due to global climate change. Inland waters are a crucial component of the global carbon cycle because they transport organic carbon from soils to oceans; bury it in sediments; and release it as carbon dioxide, yet the natural processes that oxidize organic carbon to carbon dioxide in inland waters are not well understood. This project will characterize one of the most important yet poorly constrained of these processes, the oxidation of dissolved organic carbon in sunlight when iron is present. This research, which links these mechanisms at the molecular level to broad climatic changes, will be used to inform undergraduate lesson plans that link chemical principles to earth sciences processes. Undergraduates will be engaged in summer research internships and expose them to innovative techniques in the earth sciences. The postdoctoral fellow will benefit from broadening her research perspective and methods as well as the mentoring experience gained for her future career. Complexation with iron can enhance the reactivity of organic carbon with light, resulting in the release of carbon dioxide. However, the plethora of oxidation pathways involving short-lived radical intermediates makes it difficult to predict the effects of iron. The proposed work will experimentally characterize the reaction mechanisms and reactive intermediates of iron-mediated photo-oxidation using ultrafast spectroscopy with sub-picosecond resolution. Spectroscopic characterization of the photoreactivity of model carboxylates will be paired with laboratory experiments determining the kinetics and products of iron-mediated photolysis of dissolved organic carbon collected from the East River watershed in Colorado and Arctic Long-Term Ecological Research site in Alaska. Ultimately, integrating a mechanistic understanding of the photo-oxidation of dissolved organic carbon with large-scale models of carbon fluxes may promote a more comprehensive conceptual framework of carbon dynamics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.