The Development of Environmental Comprehensive Multiphase Nuclear Magnetic Resonance Spectroscopy

Le résumé fourni par la source

Soil is the most complex mixture on this planet and is central to the transport of contaminants, carbon cycling and sustainable agriculture. However, our understanding of soil is limited in large part due to the lack of analytical approaches that can provide detail information on molecular structure and interactions in the native state. Current pre-treatment practices remove key synergies between components that are responsible for soil's reactivity, kinetics, interactions and numerous other characteristics. Nuclear magnetic resonance (NMR) spectroscopy has played an integral role in furthering soil research because of its versatility and non-destructive nature, but has not been able to study all phases of matter (solid, liquids, and gels) at once in a whole unaltered soil. Recently, comprehensive multiphase NMR (CMP-NMR) was introduced and combines traditional NMR techniques resulting in an instrument that has capabilities allowing for whole soil analysis. After an introduction of soil and NMR, the rst two research chapters focus on solving two key issues with environmental NMR, sensitivity and water suppression through experimental means. Sensitivity is increased by focusing NMR signals into one single spike and forgoing chemical shift. The result is an experiment that can determine experimental run time in low concentration samples as well as a rapid detection system for use in kinetics or dynamics. In the next chapter, a robust water suppression method is developed and applied to real environmental samples including soil by building on the current standard, SPR-W5-WATERGATE. The latter two research chapters apply CMP-NMR to soil research by rst characterizing the composition and structure of soil in its native state. It is found that aliphatic and carbohydrate components are available at the water interface while proteins from microbes and lignin are buried under the surface with hydrogen bonds and hydrophobicity playing a key role in their protection. Finally, contaminant interactions are probed in all phases where kinetics, sorption orientation, and soil binding domains are characterized in all phases. As a whole, this thesis helps to develop CMP-NMR for use in soil research and positions it as an important novel NMR technology with potential widespread application in a range of elds including materials research, biology, biochemistry and medicine.

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