RII Track-4: Molecular understanding of salt-induced selective aggregation and selective sorption of dissolved organic matter to natural particles

溶解有机物（DOM）在自然土壤、沉积物和水中普遍存在，是一种由数千种有机化合物组成的复杂混合物，主要由植物物质的腐烂产生。DOM的数量和组成影响着一系列关键的生态系统功能，并在调节土壤、地表水和海洋系统等不同环境的化学方面发挥重要作用。DOM可以选择性地与盐结合并附着在天然颗粒上，这将以复杂的方式改变它们的化学性质。该项目旨在利用太平洋西北国家实验室环境分子科学实验室（EMSL）提供的先进分析技术，确定DOM化合物的分子水平组成和特性。获得单个分子的分子水平性质将使我们能够更具体地识别DOM分子，并提高我们对其行为、命运和在环境中的运输的理解。拟议研究的结果对环境和人类健康具有直接影响，因为水和废水处理设施可以利用它来开发新的方法，以实现更有效地去除DOM的方法。除了提供使用EMSL的设施和扩大PI的研究能力外，该项目还将为PI和南卡罗来纳大学哥伦比亚分校的博士后提供培训、指导和持续的合作。技术描述DOM对天然颗粒的选择性聚集和吸附与各种环境过程高度相关，但对它们知之甚少。这种理解目前受到DOM的高度多样性和复杂性以及可用质谱仪的有限分辨率的阻碍。这一建议的智力优势在于应用超高分辨率质谱技术来识别选择性聚集或选择性吸附到自然粒子上的DOM分子，并在单个分子水平上表征其结构特性。本研究的总体目的是表征易被天然颗粒聚集或吸附的DOM化合物的分子组成和性质，以及DOM组成、盐类型和天然颗粒性质的函数。这一目标将通过使用21 T电喷雾电离超高分辨率傅里叶变换-离子回旋共振质谱（ESI-FT-ICR-MS）来表征溶液（即10 kDa）中DOM分子的分子组成和性质，并将其与Ca2+， Mg2+， Al3+和Fe3+盐以及天然粘土和金属（Fe, Mn， Al和Si）氧化物颗粒混合前后。DOM的分子水平表征将在环境分子科学实验室（EMSL）进行。EMSL人员将：协助EPSCoR-NSF研究员使用分子分析设备；提供样品分析、数据收集、分析和解释的实践培训；并提供全面的指导。EPSCoR-NSF奖学金将为PI和博士后提供一个独特的培训机会。

Non-technical DescriptionDissolved organic matter (DOM) is ubiquitous in natural soils, sediments, and waters, and is a complex mixture of several thousands of organic compounds that were produced primarily from the decay of plant matter. The amount and composition of DOM affects a range of critical ecosystem functions, and plays important roles in regulating the chemistry of environments as diverse as soils, surface waters, and marine systems. DOM can selectively combine with salts and attach to natural particles, which would change their chemical properties in complex ways. This project aims to determine the molecular-level composition and properties of DOM compounds using advanced analytical techniques available at the Environmental Molecular Sciences Laboratory (EMSL) of the Pacific Northwest National Laboratory. Obtaining molecular-level properties for individual molecules will enable more specific identification of the DOM molecules and improve our understanding of their behaviors, fate, and transport in the environment. The outcome of the proposed research has direct implications for environmental and human health as it may be used by water and wastewater treatment facilities to develop novel approaches to achieve more effective approaches for DOM removal. In addition to providing access to the facilities at EMSL and expanding the PI's research capacity, this project will provide training, mentorship, and continued collaborations for the PI and a post-doctoral fellow at the University of South Carolina at Columbia.Technical DescriptionSelective aggregation and sorption of DOM to natural particles is highly relevant to a wide variety of environmental processes, yet they are poorly understood. Such understanding is currently hampered by the high diversity and complexity of DOM and the limited resolution of available mass spectrometers. The intellectual merit of this proposal lies in the application of ultrahigh resolution mass spectroscopy techniques to identify DOM molecules that selectively aggregate or selectively sorb to natural particles and the characterization of their structural properties at the individual molecular level. The overall aim of this proposed research is to characterize the molecular composition and properties of DOM compounds susceptible to aggregation or sorption to natural particles as a function of DOM composition, salt type and natural particle properties. This aim will be achieved by characterizing the molecular composition and properties of DOM molecules in solution (that is 10 kDa) before and after mixing with salts of Ca2+, Mg2+, Al3+, and Fe3+, and natural clay and metal (Fe, Mn, Al, and Si) oxide particles using 21 T Electrospray ionization ultrahigh resolution-Fourier transform-ion cyclotron resonance-mass spectrometry (ESI-FT-ICR-MS). Molecular-level characterization of DOM will be performed at the Environmental Molecular Sciences Laboratory (EMSL). The EMSL personnel will: facilitate the EPSCoR-NSF fellow access to the molecular analysis facilities; provide hands-on training for sample analysis, data collection, analysis, and interpretation; and provide overall mentorship. This EPSCoR-NSF fellowship will provide a unique training opportunity for the PI and a postdoctoral fellow by spending time at the EMSL.