Molecular Characterization of Dissolved Organic Matter in Glacial Ice: Coupling Natural Abundance 1H NMR and Fluorescence Spectroscopy

Glaciers and ice sheets are the second largest freshwater reservoir in the global hydrologic cycle, and the onset of global climate warming has necessitated an assessment of their contributions to sea-level rise and the potential release of nutrients to nearby aquatic environments. In particular, th...

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Bibliographic Details
Published in:Environmental science & technology 2012-04, Vol.46 (7), p.3753-3761
Main Authors: Pautler, Brent G, Woods, Gwen C, Dubnick, Ashley, Simpson, André J, Sharp, Martin J, Fitzsimons, Sean J, Simpson, Myrna J
Format: Article
Language:English
Subjects:
Antarctic Regions
Applied geophysics
Arctic Regions
Earth sciences
Earth, ocean, space
Exact sciences and technology
Factor Analysis, Statistical
Ice Cover - chemistry
Internal geophysics
Magnetic Resonance Spectroscopy - methods
Organic Chemicals - analysis
Protons
Solubility
Spectrometry, Fluorescence - methods
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Summary:Glaciers and ice sheets are the second largest freshwater reservoir in the global hydrologic cycle, and the onset of global climate warming has necessitated an assessment of their contributions to sea-level rise and the potential release of nutrients to nearby aquatic environments. In particular, the release of dissolved organic matter (DOM) from glacier melt could stimulate microbial activity in both glacial ecosystems and adjacent watersheds, but this would largely depend on the composition of the material released. Using fluorescence and 1H NMR spectroscopy, we characterize DOM at its natural abundance in unaltered samples from a number of glaciers that differ in geographic location, thermal regime, and sample depth. Parallel factor analysis (PARAFAC) modeling of DOM fluorophores identifies components in the ice that are predominantly proteinaceous in character, while 1H NMR spectroscopy reveals a mixture of small molecules that likely originate from native microbes. Spectrofluorescence also reveals a terrestrial contribution that was below the detection limits of NMR; however, 1H nuclei from levoglucosan was identified in Arctic glacier ice samples. This study suggests that the bulk of the DOM from these glaciers is a mixture of biologically labile molecules derived from microbes.
ISSN:0013-936X
1520-5851
DOI:10.1021/es203942y