Role of Organic Matter in Determining the Solubility of Atmospherically-Delivered Iron

大气向海洋输送可溶性铁是促进海洋初级生产和减少大气CO2的重要过程。燃烧影响空气团携带高可溶性铁，但尽管对全球碳循环很重要，但这种溶解性增加的原因仍不清楚。酸性有机物（OM）组分（例如-COOH基团）可以与微量金属络合，但迄今为止还没有研究调查气溶胶OM的综合分子特征，以确定它们作为铁溶解度的决定因素。在这个项目中，Old Dominion大学的研究人员将研究海洋气溶胶水溶性OM （WSOM）的分子特征与铁溶解度之间的关系。在GEOTRACES巡航期间收集的海洋颗粒气溶胶将被检查，以确定WSOM的特征，这些特征可能在向北大西洋输送可溶性和生物可利用的铁方面发挥作用。气溶胶WSOM将使用先进的分子和化学计量学技术进行表征，以测试：(1)大陆燃烧影响的气溶胶样品是否显示出与大陆尘埃影响样品不同的分子特征，其特征与具有酸性官能团的OM的较高贡献一致；(2)气溶胶WSOM沿铁溶解度梯度的变化表明，高氧化合物的相对大小和酸性官能团的贡献同时发生变化；(3)二维HMBC核磁共振揭示了陆源燃烧影响的复合样品相对于海洋和粉尘影响的样品中独特的成分，这些独特的成分包括具有羧基官能团的OM，可以结合铁。该项目将是第一个广泛研究WSOM分子特征和Fe在同时收集的气溶胶样品上的溶解度的项目。研究结果将有助于了解海洋中铁的分布和生物地球化学循环。这一提议的一个潜在的变革方面将是鉴定气溶胶WSOM分子组分独特的燃烧影响的气团，有可能促进气溶胶铁溶解度。更广泛的影响：本项目的发现预计将与海洋和全球生物地球化学循环高度相关的OM和许多形成有机配合物的微量金属。受燃烧影响的有机质关联可能有助于解释其他微量金属的全球海洋分布模式，并为海洋过程（例如初级生产、生物泵）提供关键见解。该项目将为ODU的pi和本科生和研究生提供一个强有力的跨学科培训和学习环境。博士生将参与项目的各个方面，学习最先进的分析技术，并获得项目管理、数据处理和数据展示方面的经验

The atmospheric delivery of soluble Fe to the ocean is an important process contributing to oceanic primary production and the drawdown of atmospheric CO2. Combustion influenced air masses carry highly soluble Fe, but the reasons for this increased solubility remain unclear despite the importance to global carbon cycling. Acidic organic matter (OM) components (e.g., -COOH groups) can complex with trace metals, yet no study to date has investigated the comprehensive molecular characteristics of aerosol OM for their role as a determinant of Fe solubility. In this project, researchers at Old Dominion University will study the relationship between the molecular characteristics of marine aerosol water soluble OM (WSOM) and Fe solubility. Marine particulate aerosols collected during GEOTRACES cruises will be examined to identify WSOM characteristics that may play a role in delivering soluble and bioavailable Fe to the N. Atlantic Ocean. Aerosol WSOM will be characterized using advanced molecular and chemometric techniques to test whether: (1) continental combustion-influenced aerosol samples show molecular characteristics unique from those of continental dust influenced samples, having characteristics consistent with higher contributions from OM with acidic functional group; (2) aerosol WSOM examined along a gradient of Fe solubility show concurrent changes in the relative magnitude of highly oxygenated compounds and contributions from acidic functional groups; and (3) 2D HMBC NMR reveal unique components in composite continental combustion influenced samples relative to marine and dust-influenced samples, and these unique components include OM with carboxyl functional groups that can bind Fe. This project will be the first of its kind to extensively examine WSOM molecular characteristics and Fe solubility on concurrently collected aerosol samples. The results will be useful for understanding Fe distributions and biogeochemical cycling in the ocean. A potentially transformative aspect of this proposal will be the identification of aerosol WSOM molecular components unique to combustion influenced air masses that have the potential to facilitate aerosol Fe solubility. Broader Impacts: The findings of this project are expected to be highly relevant to oceanic and global biogeochemical cycling of OM and many trace metals that form organic complexes. Combustion-influenced OM associations may help explain patterns in the global oceanic distribution of other trace metals and provide key insights into oceanic processes (e.g., primary production, biological pump). The project would provide a strong interdisciplinary, training and learning environment for the PIs and undergraduate and graduate students at ODU. A PhD student would be involved in all aspects of the project and learn state-of-the-art analytical techniques and gain experience in aspects of project management, data processing, and data presentation