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

Claresta Joe-Wong博士已获得博士后奖学金，在劳伦斯伯克利国家实验室工作，了解大气和内陆沃茨之间的碳循环，这是由于全球气候变化越来越重要。内陆沃茨是全球碳循环的一个重要组成部分，因为它们将有机碳从土壤输送到海洋;将其埋在沉积物中;并将其作为二氧化碳释放出来，但人们对内陆沃茨中有机碳氧化为二氧化碳的自然过程并不十分了解。该项目将描述这些过程中最重要但限制性最差的过程之一，即当铁存在时溶解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，将用于通知将化学原理与地球科学过程联系起来的本科课程计划。本科生将参加暑期研究实习，并使他们接触到地球科学的创新技术。博士后研究员将受益于扩大她的研究视角和方法，以及为她未来的职业生涯所获得的指导经验。与铁络合可以增强有机碳与光的反应性，导致二氧化碳的释放。然而，过多的氧化途径涉及短寿命的自由基中间体，使其难以预测铁的影响。本论文将利用亚皮秒分辨率的超快光谱技术对铁离子光氧化反应机理和反应中间体进行实验研究。光谱表征的模型羧酸盐的光反应性将配对与实验室实验确定的动力学和产品的铁介导的溶解有机碳的光解收集从东河流域在科罗拉多和北极长期生态研究网站在阿拉斯加。最终，将溶解有机碳的光氧化机理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NSF的法定使命，并被认为值得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来支持。

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.