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

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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.