Structural Characterization of Freshwater Dissolved Organic Matter from Arctic and Temperate Climates Using Novel Analytical Approaches
Dissolved organic matter (DOM) is comprised of a complex array of molecular constituents that are linked to many globally-relevant processes and yet this material is still largely molecularly uncharacterized. Research presented here attempted to probe the molecular complexity of this material from b...
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ftunivtoronto:oai:localhost:1807/35160 2023-05-15T14:55:23+02:00 Structural Characterization of Freshwater Dissolved Organic Matter from Arctic and Temperate Climates Using Novel Analytical Approaches Woods, Gwen Simpson, Andre Chemistry WITHHELD_ONE_YEAR http://hdl.handle.net/1807/35160 en_ca eng http://hdl.handle.net/1807/35160 dissolved organic matter nuclear magnetic resonance Arctic terpenoid-derived sterols high performance liquid chromatography 0425 0485 Thesis ftunivtoronto 2020-06-17T11:22:05Z Dissolved organic matter (DOM) is comprised of a complex array of molecular constituents that are linked to many globally-relevant processes and yet this material is still largely molecularly uncharacterized. Research presented here attempted to probe the molecular complexity of this material from both Arctic and temperate climates via multifaceted and novel approaches. DOM collected from remote Arctic watersheds provided evidence to suggest that permafrost-disturbed systems contain more photochemically- and biologically-labile material than undisturbed systems. These results have large implications for predicted increasing temperatures where widespread permafrost melt would significantly impact stores of organic carbon in polar environments. In attempting to address the complexities and reactivity of DOM within global environments, more information at the molecular-level is necessary. Further research sought to unravel the molecularly uncharacterized fraction via use of nuclear magnetic resonance (NMR) spectroscopy in conjunction with hyphenated and varied analytical techniques. Directly hyphenated high performance size exclusion chromatography (HPSEC) with NMR was explored. This hyphenation was found to separate DOM into structurally distinct fractions but proved limited at reducing DOM heterogeneity. Of the many high performance liquid chromatography (HPLC) techniques tested, hydrophilic interaction chromatography (HILIC) was found the most effective at simplifying DOM. HILIC separations utilizing a sample from Florida resulted in fractions with highly resolved NMR signals and substantial reduction in heterogeneity. Further development with a 2D-HILIC/HILIC system to achieve additional fractionation was employed. This method produced fractions of DOM that were homogenous enough to produce excellent resolution and spectral dispersion, permitting 2D and 3D NMR experiments to be performed. Extensive NMR analyses of these fractions demonstrated strong evidence for the presence of highly oxidized sterols. All fractions, however, provided 2D NMR spectra consistent with oxidized polycyclic structures and support emerging data and hypotheses suggesting that cyclic structures, likely derived from terpenoids, are an abundant, refractory and major component of DOM. Research presented within this thesis demonstrates that HILIC and NMR are excellent co-techniques for the analysis of DOM as well as that oxidized sterols and other cyclic components with significant hydroxyl and carboxyl substituents are major constituents in DOM. PhD Thesis Arctic permafrost University of Toronto: Research Repository T-Space Arctic |
institution |
Open Polar |
collection |
University of Toronto: Research Repository T-Space |
op_collection_id |
ftunivtoronto |
language |
English |
topic |
dissolved organic matter nuclear magnetic resonance Arctic terpenoid-derived sterols high performance liquid chromatography 0425 0485 |
spellingShingle |
dissolved organic matter nuclear magnetic resonance Arctic terpenoid-derived sterols high performance liquid chromatography 0425 0485 Woods, Gwen Structural Characterization of Freshwater Dissolved Organic Matter from Arctic and Temperate Climates Using Novel Analytical Approaches |
topic_facet |
dissolved organic matter nuclear magnetic resonance Arctic terpenoid-derived sterols high performance liquid chromatography 0425 0485 |
description |
Dissolved organic matter (DOM) is comprised of a complex array of molecular constituents that are linked to many globally-relevant processes and yet this material is still largely molecularly uncharacterized. Research presented here attempted to probe the molecular complexity of this material from both Arctic and temperate climates via multifaceted and novel approaches. DOM collected from remote Arctic watersheds provided evidence to suggest that permafrost-disturbed systems contain more photochemically- and biologically-labile material than undisturbed systems. These results have large implications for predicted increasing temperatures where widespread permafrost melt would significantly impact stores of organic carbon in polar environments. In attempting to address the complexities and reactivity of DOM within global environments, more information at the molecular-level is necessary. Further research sought to unravel the molecularly uncharacterized fraction via use of nuclear magnetic resonance (NMR) spectroscopy in conjunction with hyphenated and varied analytical techniques. Directly hyphenated high performance size exclusion chromatography (HPSEC) with NMR was explored. This hyphenation was found to separate DOM into structurally distinct fractions but proved limited at reducing DOM heterogeneity. Of the many high performance liquid chromatography (HPLC) techniques tested, hydrophilic interaction chromatography (HILIC) was found the most effective at simplifying DOM. HILIC separations utilizing a sample from Florida resulted in fractions with highly resolved NMR signals and substantial reduction in heterogeneity. Further development with a 2D-HILIC/HILIC system to achieve additional fractionation was employed. This method produced fractions of DOM that were homogenous enough to produce excellent resolution and spectral dispersion, permitting 2D and 3D NMR experiments to be performed. Extensive NMR analyses of these fractions demonstrated strong evidence for the presence of highly oxidized sterols. All fractions, however, provided 2D NMR spectra consistent with oxidized polycyclic structures and support emerging data and hypotheses suggesting that cyclic structures, likely derived from terpenoids, are an abundant, refractory and major component of DOM. Research presented within this thesis demonstrates that HILIC and NMR are excellent co-techniques for the analysis of DOM as well as that oxidized sterols and other cyclic components with significant hydroxyl and carboxyl substituents are major constituents in DOM. PhD |
author2 |
Simpson, Andre Chemistry |
format |
Thesis |
author |
Woods, Gwen |
author_facet |
Woods, Gwen |
author_sort |
Woods, Gwen |
title |
Structural Characterization of Freshwater Dissolved Organic Matter from Arctic and Temperate Climates Using Novel Analytical Approaches |
title_short |
Structural Characterization of Freshwater Dissolved Organic Matter from Arctic and Temperate Climates Using Novel Analytical Approaches |
title_full |
Structural Characterization of Freshwater Dissolved Organic Matter from Arctic and Temperate Climates Using Novel Analytical Approaches |
title_fullStr |
Structural Characterization of Freshwater Dissolved Organic Matter from Arctic and Temperate Climates Using Novel Analytical Approaches |
title_full_unstemmed |
Structural Characterization of Freshwater Dissolved Organic Matter from Arctic and Temperate Climates Using Novel Analytical Approaches |
title_sort |
structural characterization of freshwater dissolved organic matter from arctic and temperate climates using novel analytical approaches |
publishDate |
|
url |
http://hdl.handle.net/1807/35160 |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic permafrost |
genre_facet |
Arctic permafrost |
op_relation |
http://hdl.handle.net/1807/35160 |
_version_ |
1766327177347858432 |